Simple code c

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Simple code c

Small & Simple Programs in C

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Let’s first start with very small & simple programs to get basic idea of C programming code structure. We shall get the basic idea of variable declaration, scanning and printing etc.

Basic Programs

We shall see the classic «Hello World!» program to get an insight of how a program is written in c. We have programs on variables available in c. These are most commonly used elementary variables. Also, we shall see how arithmetic operations can be performed in a c program.

General Programs

There are programs which we use in our routine, or say a programmer’s routine. These programs are easy to understand and should help in understanding style of C programming. We shall see here some of these programs and some cool tricks.

C Programming Examples

C is a general-purpose procedural programming language mainly used for software development such as operating systems, compilers, language interpreters, databases, etc. The main features of C programming are speed and efficiency, modularity, portability, static typing, and extensibility. C programming is the perfect language for beginners to learn programming.

This section contains many examples of C programming, from simple programs to very complex and advanced C programs. These C Programming examples are categorized as data types, array, pointers, matrix, bitwise operations, control flow statements, math functions, file handling, factorial and Fibonacci series, palindrome, strings, searching, Sorting, etc. You can also explore a collection of data structure programs in trees, binary trees, heaps, linked lists, hash tables, graphs, stacks, and queues. Each sample program includes a program description, C code, and program output. All examples have been compiled and tested on Windows and Linux systems.

Simple code c

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Tutorial: Create a simple C# console app in Visual Studio (part 1 of 2)

In this tutorial, you use Visual Studio to create and run a C# console app, and explore some features of the Visual Studio integrated development environment (IDE). This tutorial is part 1 of a two-part tutorial series.

In this tutorial, you:

In part 2, you extend this app to add more projects, learn debugging tricks, and reference third-party packages.

Prerequisites

You must have Visual Studio installed.

If you haven’t already installed Visual Studio, go to the Visual Studio downloads page to install it for free.

Create a project

To start, create a C# application project. The project type comes with all the template files you need.

Open Visual Studio, and choose Create a new project in the Start window.

In the Create a new project window, choose C# from the Language list. Next, choose Windows from the Platform list and Console from the project types list.

After you apply the language, platform, and project type filters, choose the Console Application template, and then select Next.

If you don’t see the Console Application template, select Install more tools and features.

Then, in the Visual Studio Installer, choose the .NET Core cross-platform development workload.

After that, choose the Modify button in the Visual Studio Installer. You might be prompted to save your work; if so, do so. Next, choose Continue to install the workload. Then, return to step 2 in this «Create a project» procedure.

In the Configure your new project window, type or enter Calculator in the Project name box. Then, choose Next.

In the Additional information window, .NET Core 3.1 should already be selected for your target framework. If not, select .NET Core 3.1. Then, choose Create.

Visual Studio opens your new project, which includes default «Hello World» code. To view it in the editor, select the code file Program.cs in the Solution Explorer window, which is typically on the right-hand side of Visual Studio.

The default «Hello World» code calls the WriteLine method to display the literal string «Hello, World!» in the console window. If you press F5, you can run the default program in Debug mode. After the application runs in the debugger, the console window stays open. Press any key to close the console window.

Open Visual Studio, and choose Create a new project in the Start window.

In the Create a new project window, select All languages, and then choose C# from the dropdown list. Choose Windows from the All platforms list, and choose Console from the All project types list.

After you apply the language, platform, and project type filters, choose the Console App template, and then select Next.

If you don’t see the Console App template, select Install more tools and features.

In the Visual Studio Installer, choose the .NET desktop development workload, and then select Modify.

In the Configure your new project window, type or enter Calculator in the Project name box, and then select Next.

In the Additional information window, .NET 6.0 should already be selected for your target framework. Select Create.

Visual Studio opens your new project, which includes default «Hello World» code.

To view it in the editor, select the code file Program.cs in the Solution Explorer window, which is typically on the right-hand side of Visual Studio.

The single code statement calls the WriteLine method to display the literal string «Hello, World!» in the console window. If you press F5, you can run the default program in Debug mode. After the application runs in the debugger, the console window stays open. Press any key to close the console window.

Create the app

In this section, you:

Explore integer math

Start with some basic integer math in C#.

In the code editor, delete the default «Hello World» code.

In its place, type the following code:

Notice that when you do so, the IntelliSense feature in Visual Studio offers you the option to autocomplete the entry.

Choose the green Start button next to Calculator to build and run your program, or press F5.

A console window opens that reveals the sum of 42 + 119, which is 161.

Close the console window.

In Solution Explorer, in the right pane, select Program.cs to display the file in the code editor

Replace the line with the following code:

If you type the code, the Visual Studio IntelliSense feature offers you the option to autocomplete the entry.

To build and run your app, press F5, or select the green arrow next to the name Calculator in the top toolbar.

A console window opens that shows the sum of 42 + 119, which is 161.

Close the console window.

Add code to create a calculator

Continue by adding a more complex set of calculator code to your project.

In the code editor, replace all the code in program.cs with the following new code:

Select the Calculator button or press F5 to run your app.

A console window opens.

In the console window, follow the prompts to add the numbers 42 and 119 together.

Your app should look similar to the following screenshot:

In the code editor, replace all the code in program.cs with the following new code:

Select the Calculator button or press F5 to run your app.

A console window opens.

In the console window, follow the prompts to add the numbers 42 and 119 together.

Your app should look similar to the following screenshot:

Add decimal functionality

Now, tweak the code to add more functionality.

The current calculator app only accepts and returns whole numbers. For example, if you run the app and divide the number 42 by the number 119, your result is zero, which isn’t exact.

To fix the code to improve precision by handling decimals:

From program.cs in the Visual Studio editor, press Ctrl+H to open the Find and Replace control.

Type int in the control, and type float in the Replace field.

Select the icons for Match case and Match whole word in the control, or press Alt+C and Alt+W.

Select the Replace all icon or press Alt+A to run the search and replace.

Run your calculator app again, and divide the number 42 by the number 119.

The app now returns a decimal number instead of zero.

Now the app can produce decimal results. Make a few more tweaks to the code so the app can calculate decimals too.

Run your calculator app, and divide the number 42.5 by the number 119.75.

The app now accepts decimal values, and returns a longer decimal numeral as its result.

In the Revise the code section, you reduce the number of decimal places in the results.

Debug the app

You’ve improved your basic calculator app, but your app doesn’t yet handle exceptions, such as user input errors. For example, if users try to divide by zero, or enter an unexpected character, the app might stop working, return an error, or return an unexpected nonnumeric result.

Let’s walk through a few common user input errors, locate them in the debugger if they appear there, and fix them in the code.

For more information about the debugger and how it works, see First look at the Visual Studio debugger.

Fix the «divide by zero» error

If you try to divide a number by zero, the console app might freeze, and then shows you what’s wrong in the code editor.

Sometimes the app doesn’t freeze, and the debugger doesn’t show a divide-by-zero error. Instead, the app might return an unexpected nonnumeric result, such as an infinity symbol. The following code fix still applies.

To change the code to handle this error:

In program.cs, replace the code between case «d»: and the comment that says // Wait for the user to respond before closing with the following code:

After you replace the code, the section with the switch statement should look similar to the following screenshot:

Now, when you divide any number by zero, the app asks for another number, and keeps asking until you provide a nonzero number.

Fix the «format» error

If you enter an alphabetic character when the app expects a numeric character, the app freezes. Visual Studio shows you what’s wrong in the code editor.

To prevent this exception, you can refactor the code you’ve previously entered.

Revise the code

The Calculator class handles the bulk of the calculation work, and the Program class handles the user interface and error-handling work.

Let’s get started.

In program.cs, delete everything in the Calculator namespace between its opening and closing braces:

Between the braces, add the following new Calculator class:

Also add a new Program class, as follows:

Select the Calculator button or press F5 to run your app.

Follow the prompts and divide the number 42 by the number 119. Your results should look similar to the following screenshot:

You can now enter more equations until you choose to close the console app. There are also fewer decimal places in the results. And if you enter an incorrect character, you get an appropriate error response.

Close the app

If you haven’t already done so, close the Calculator app.

Close the Output pane in Visual Studio.

In Visual Studio, press Ctrl+S to save your app.

Add Git source control

Now that you’ve created an app, you might want to add it to a Git repository. Visual Studio makes that process easy with Git tools you can use directly from the IDE.

Git is the most widely used modern version control system, so whether you’re a professional developer or you’re learning how to code, Git can be very useful. If you’re new to Git, the https://git-scm.com/ website is a good place to start. There, you can find cheat sheets, a popular online book, and Git Basics videos.

To associate your code with Git, start by creating a new Git repository where your code is located:

In the status bar at the bottom-right corner of Visual Studio, select Add to Source Control, and then select Git.

In the Create a Git repository dialog box, sign in to GitHub.

The repository name auto-populates based on your folder location. Your new repository is private by default, which means you’re the only one who can access it.

Whether your repository is public or private, it’s best to have a remote backup of your code stored securely on GitHub. Even if you aren’t working with a team, a remote repository makes your code available to you from any computer.

Select Create and Push.

After you create your repository, you see status details in the status bar.

The first icon with the arrows shows how many outgoing/incoming commits are in your current branch. You can use this icon to pull any incoming commits or push any outgoing commits. You can also choose to view these commits first. To do so, select the icon, and then select View Outgoing/Incoming.

The second icon with the pencil shows the number of uncommitted changes to your code. You can select this icon to view those changes in the Git Changes window.

To learn more about how to use Git with your app, see the Visual Studio version control documentation.

Review: Code complete

In this tutorial, you made many changes to the calculator app. The app now handles computing resources more efficiently, and handles most user input errors.

Here’s the complete code, all in one place:

Next steps

Continue with the second part of this tutorial:

C programs

C programs with output showing usage of operators, loops, functions, arrays, performing operations on strings, files, pointers. Download executable files and execute them without compiling the source file. Code::Blocks IDE is used to write programs; most of these will work with GCC and Dev C++ compilers. The first program, prints «Hello World.»

C programming examples with output

Output of program:
«Hello World»

Output:
Input an integer
7897
The integer is: 7897

Output:
Enter a number
-45
Less than or equal to zero.

How to compile C programs with GCC compiler?

If you are using GCC on Linux operating system, then you may need to modify the programs. For example, consider the following program that prints the first ten natural numbers.

and calls the getch function, but this file is Borland specific, so it works in Turbo C compiler but not in GCC. The program for GCC must be like:

Simple C# code examples with output (Console application example)

Hello world program in c#

Let’s start with basic C# program which is printing «hello world» in console application in C#. You can consider working on Visual Studio IDE, but i will be using online IDE (dotnetfiddle), so you can play with the code, if needed.

In Visual Studio, if you have downloaded Visual Studio Community version, you can open «File»-> «New»-> «Project», then Select «Console Application» ( Search «Console» in top-right, if you cannot find it), name it «Hello World» and click «OK»

Here is the simple C# code to print Hello World

In the above code, we have imported a namespace » System «, using is a keyword, highlighted with blue by the editor, by ‘using’ keyword, we import Class or namespace.

If you have created program in Visual Studio you will see one extra line » namespace ConsoleApp1 «, basically this is the namespace of this Class » Program «

Now, next line of code is » public class program «, as C# is an Object Oriented language, every line of code that actually does something, is wrapped inside a class. In this case, the class is simply called Program.

public = access modifier in C#, means this class can be accessed publicly from anywhere in the application.

program = name of the console application, which can be anything.

Now, let’s understand next line of code » public static void Main(string[] args) «, i will explain keywords and it’s meaning one by one.

public = again, access modifier of C#, public means it is can be accessed publicly from anywhere in the application.

static = this is another keyword in C#, here static defines that this class method, can be called without needing of the object ( you will learn more about Class/Object in Here ), basically we create objects of class and then call methods inside the class using those objects created by us, but as this method is defined as «static», it doesn’t need to called using Class Object.

void = return type of method, means this method will return anything, some methods can return data-type like int, string etc., but as this method returns nothing so «void» is used.

Main = method name,this method is the entry-point of our application, that is, the first piece of code to be executed, and in our example, the only method to be executed.

string[] args= argument passed to method, which is string array, which is used to store the command line arguments. Writing this is optional.

Now, the last line of code » Console.WriteLine(«Hello World»); «, this line basically, prints ‘hello world’ on the console, Console.WriteLine is method in «System» namespace which is used here and «Hello World» is passed as a string argument inside this method.

Check if a number is prime in C#

Prime number is a number which is divisible by itself or 1, so we will apply logic to get number by user.

We will divide it by 2, get remainder value and loop it using for loop until we reach the remainder value, deivide each number modulu 2, each value from 2 to remainder value, if number remainder is 0 then it is not prime and set flag =1, else flag =0 and number is prime.

I have explained code line by line using comments, please do read them to understand it easily.

C# Program to check if given number is odd or even

In this program, we will ask user a number and then we will check if user inputed number is even or odd

In the above code, we are asking user to Enter a number, then we are reading it using Console.Readline, once we have the number we try to get modulus ( % ) or remainder of that number if it is 0, then it is Even else odd number.

Check if string is palindrome in C#

Palindrome string is a string, in which if we reverse the string and it still remains same, then it is a palindrome string.

While looping, we start from last character of string and then append it with second last character and so on, until string is empty.

Once we are done, we match it with intial string, if both are same, then string is palindrome.

Check if int is palindrome or not in C#

Checking if int is palindrome or not, is much easier than checking string, here is the code for it.

I have explained code using comments.

Printing right angle triangle pattern using * in C#

In the above code, we are using two for loops.

Loop 1 runs until the value of i is less than or equal to 6, means we will be creating 6 rows to print star.

Loop 2 prints star’s, whenever this loop is executed, it will print 1 column for 1st row, as value of i =1, and j =1, when value of i=2, it will print 2 times, as loop can run twice and so on.

Swap two numbers using third variable in C#

In the above code, we are swapping number using third temporary variable.

Printing fibonacci series in C#

In the above code, we are initializing three variable, one for asking user maximum number for fibonacci series, second is for saving previous number from current number and third variable to save next number.

Once, we have the number, we loop until the max. number using for loop and print the sum of next and previous value.

C# program to search an element in an array

In this program, we will be using a basic C# linear search, to search an element in an array.

In the above code, we have created a string array and then using for loop we are looping each element of an array to check if it is our required item or not.

If an item is found, we are setting the flag » ItemFound » to true.

Simple code c

Tutorial: Create a simple C# console app in Visual Studio (part 1 of 2)

In this tutorial, you:

In part 2, you extend this app to add more projects, learn debugging tricks, and reference third-party packages.

You must have Visual Studio installed.

If you haven’t already installed Visual Studio, go to the Visual Studio downloads page to install it for free.

Create a project

To start, create a C# application project. The project type comes with all the template files you need.

Open Visual Studio, and choose Create a new project in the Start window.

In the Create a new project window, choose C# from the Language list. Next, choose Windows from the Platform list and Console from the project types list.

After you apply the language, platform, and project type filters, choose the Console Application template, and then select Next.

[!NOTE] If you don’t see the Console Application template, select Install more tools and features.

Then, in the Visual Studio Installer, choose the .NET Core cross-platform development workload.

In the Configure your new project window, type or enter Calculator in the Project name box. Then, choose Next.

. image type=»content» source=»./media/vs-2019/csharp-name-your-calculator-project.png» alt-text=»Screenshot that shows naming your project ‘Calculator’ in the ‘Configure your new project’ window.».

In the Additional information window, .NET Core 3.1 should already be selected for your target framework. If not, select .NET Core 3.1. Then, choose Create.

The default «Hello World» code calls the xref:System.Console.WriteLine%2A method to display the literal string «Hello, World!» in the console window. If you press F5, you can run the default program in Debug mode. After the application runs in the debugger, the console window stays open. Press any key to close the console window.

Open Visual Studio, and choose Create a new project in the Start window.

After you apply the language, platform, and project type filters, choose the Console App template, and then select Next.

[!NOTE] If you don’t see the Console App template, select Install more tools and features.

In the Visual Studio Installer, choose the .NET desktop development workload, and then select Modify.

In the Configure your new project window, type or enter Calculator in the Project name box, and then select Next.

In the Additional information window, .NET 6.0 should already be selected for your target framework. Select Create.

Visual Studio opens your new project, which includes default «Hello World» code.

To view it in the editor, select the code file Program.cs in the Solution Explorer window, which is typically on the right-hand side of Visual Studio.

The single code statement calls the xref:System.Console.WriteLine%2A method to display the literal string «Hello, World!» in the console window. If you press F5, you can run the default program in Debug mode. After the application runs in the debugger, the console window stays open. Press any key to close the console window.

In this section, you:

Explore integer math

Start with some basic integer math in C#.

In its place, type the following code:

Notice that when you do so, the IntelliSense feature in Visual Studio offers you the option to autocomplete the entry.

Choose the green Start button next to Calculator to build and run your program, or press F5.

A console window opens that reveals the sum of 42 + 119, which is 161.

In Solution Explorer, in the right pane, select Program.cs to display the file in the code editor

Replace the line with the following code:

If you type the code, the Visual Studio IntelliSense feature offers you the option to autocomplete the entry.

To build and run your app, press F5, or select the green arrow next to the name Calculator in the top toolbar.

A console window opens that shows the sum of 42 + 119, which is 161.

Close the console window.

Add code to create a calculator

Continue by adding a more complex set of calculator code to your project.

. moniker range=» =vs-2022″

In the code editor, replace all the code in program.cs with the following new code:

Select the Calculator button or press F5 to run your app.

A console window opens.

In the console window, follow the prompts to add the numbers 42 and 119 together.

Your app should look similar to the following screenshot:

Add decimal functionality

Now, tweak the code to add more functionality.

The current calculator app only accepts and returns whole numbers. For example, if you run the app and divide the number 42 by the number 119, your result is zero, which isn’t exact.

To fix the code to improve precision by handling decimals:

From program.cs in the Visual Studio editor, press Ctrl+H to open the Find and Replace control.

Type int in the control, and type float in the Replace field.

Select the icons for Match case and Match whole word in the control, or press Alt+C and Alt+W.

Select the Replace all icon or press Alt+A to run the search and replace.

Run your calculator app again, and divide the number 42 by the number 119.

The app now returns a decimal number instead of zero.

Now the app can produce decimal results. Make a few more tweaks to the code so the app can calculate decimals too.

Run your calculator app, and divide the number 42.5 by the number 119.75.

The app now accepts decimal values, and returns a longer decimal numeral as its result.

In the Revise the code section, you reduce the number of decimal places in the results.

Let’s walk through a few common user input errors, locate them in the debugger if they appear there, and fix them in the code.

[!TIP] For more information about the debugger and how it works, see First look at the Visual Studio debugger.

Fix the «divide by zero» error

If you try to divide a number by zero, the console app might freeze, and then shows you what’s wrong in the code editor.

[!NOTE] Sometimes the app doesn’t freeze, and the debugger doesn’t show a divide-by-zero error. Instead, the app might return an unexpected nonnumeric result, such as an infinity symbol. The following code fix still applies.

To change the code to handle this error:

In program.cs, replace the code between case «d»: and the comment that says // Wait for the user to respond before closing with the following code:

After you replace the code, the section with the switch statement should look similar to the following screenshot:

Now, when you divide any number by zero, the app asks for another number, and keeps asking until you provide a nonzero number.

Fix the «format» error

If you enter an alphabetic character when the app expects a numeric character, the app freezes. Visual Studio shows you what’s wrong in the code editor.

To prevent this exception, you can refactor the code you’ve previously entered.

Revise the code

The Calculator class handles the bulk of the calculation work, and the Program class handles the user interface and error-handling work.

Let’s get started.

In program.cs, delete everything in the Calculator namespace between its opening and closing braces:

Between the braces, add the following new Calculator class:

Also add a new Program class, as follows:

Select the Calculator button or press F5 to run your app.

Follow the prompts and divide the number 42 by the number 119. Your results should look similar to the following screenshot:

If you haven’t already done so, close the Calculator app.

Close the Output pane in Visual Studio.

In Visual Studio, press Ctrl+S to save your app.

Review: Code complete

In this tutorial, you made many changes to the calculator app. The app now handles computing resources more efficiently, and handles most user input errors.

Here’s the complete code, all in one place:

Continue with the second part of this tutorial:

Playjasb2/Simple-C-Compiler

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README.md

Simple C Compiler •

As a side project, I have decided to build a compiler that would compile a simplified version of C, that I call «Simple C», to x86-64.

As of right now, the definition of this language isn’t fully layed out, since more features will be added overtime. Simple C is currently «headerless», as I’m not going to process header files from the start. This means, for the language to do anything particularly useful, such as printing to stdout or taking input with stdin, I will make the assumption that those behaviours are defined, as if stdio.h is built-in. Over time, this may subject to change.

Note: I have only tested the compiler on macOS and Linux; I have not tested it on Windows.

In order to compile the compiler and optionally install it in your system, you need the following installed in your system:

CMake is a build system that I decided to use that would work cross-platform, and I found it to be quite useful for large projects, such as this, in order to help me easily define my build pipeline.

Building and Installing the Compiler

Once you have those prerequisites and you have cloned the repository, go into the repository using the Terminal, and execute the following commands:

This will make a build directory in the repo folder, and cd into it. And then running the cmake command on the parent folder will bring compiler source files into the build folder and generate a Makefile, based on the build pipeline that I have defined in my CMakeLists.txt files that I have, throughout my project.

To build the executables, you just need to execute make while you’re in the build folder, and it will generate the executables for both the compiler, and the test program for it.

As of right now, I have not finished setting up a pipeline for testing. I currently have a test program that would look a specific test file, and run the lexer on it. I still have to set up more test cases that would test how each phases of the compiler interpret each feature of the source language. I also plan to test everything using CTest, and have CI be used in this project, where I may use Github Actions to automate the testing that would be done, every time I commit to the repo.

About

A compiler to compile a simplified version of C

3 Simple C++17 Features That Will Make Your Code Simpler

This article is a guest post written by guest author jft.

C++17 has brought a lot of features to the C++ language. Let’s dig into three of them that help make coding easier, more concise, intuitive and correct.

We’ll begin with Structured Bindings. These were introduced as a means to allow a single definition to define multiple variables with different types. Structured bindings apply to many situations, and we’ll see several cases where they can make code more concise and simpler.

Then we’ll see Template Argument Deduction, which allows us to remove template arguments that we’re used to typing, but that we really shouldn’t need to.

And we’ll finish with Selection Initialization, which gives us more control about object scoping and lets us define values where they belong.

So let’s start with structured bindings.

Structured Bindings

Structured Bindings allow us to define several objects in one go, in a more natural way than in the previous versions of C++.

From C++11 to C++17

Consider the function:

This returns three variables all of different types. To access these from a calling function prior to C++17, we would need something like:

Where the variables have to be defined before use and the types known in advance.

But using Structured Bindings, we can simply do this as:

which is a much nicer syntax and is also consistent with modern C++ style using auto almost whenever possible.

Returning compound objects

This is the easy way to assign the individual parts of a compound type (such as a struct, pair etc) to different variables all in one go – and have the correct types automatically assigned. So let’s have a look at an example. If we insert into a map, then the result is a std::pair :

And if anyone is wondering why the types are not explicitly stated for pair, then the answer is Template Argument Deduction in C++17 – keep reading!

So to determine if the insert was successful or not, we could extract the info from what the insert method returned:

As a sneak peek into the last section, as C++17 now has Selection Initialization, then we could (and probably would) write this as:

But more on this in a moment.

Iterating over a compound collection

Structured Bindings also work with range-for as well. So considering the previous mymap definition, prior to C++17 we would iterate it with code looking like this:

Or maybe, to be more explicit:

But Structured Bindings allow us to write it more directly:

The usage of the variables key and value are more instructive than entry.first and entry.second – and without requiring the extra variable definitions.

Direct initialization

But as Structured Bindings can initialize from a tuple, pair etc, can we do direct initialization this way?

Yes we can. Consider:

Using Structured Bindings, this can be written as:

Is this really an improvement over the previous definition? OK, we’ve done in one line what would have taken three but why would we want to do this?

Consider the following code:

Both iss and name are only used within the for block, yet iss has to be declared outside of the for statement and within its own block so that the scope is limited to that required.

This is weird, because iss belongs to the for loop.

Initialization of multiple variables of the same type has always been possible. For example:

But what we’d like to write – but can’t – is:

With Structured Bindings we can write:

Which allows the variables iss and name (and i and ch ) to be defined within the scope of the for statement as needed and also their type to be automatically determined.

And likewise with the if and switch statements, which now take optional Selection Initialization in C++17 (see below). For example:

Note that we can’t do everything with structured bindings, and trying to fit them in to every situation can make the code more convoluted. Consider the following example:

But we can’t because a variable declared within an auto type specifier cannot appear within its own initializer! Which is kind of understandable.

So to sum up, the advantages of using Structured Bindings are:

The drawback, of course, is that an intermediary (eg std::pair ) is used. This needn’t necessarily impact upon performance (it is only done once at the start of the loop anyhow) as move semantics would be used where possible – but note that where a type used is non-moveable (eg like std::array ) then this could incur a performance ‘hit’ depending upon what the copy operation involved.

But don’t pre-judge the compiler and pre-optimize code! If the performance isn’t as required, then use a profiler to find the bottleneck(s) – otherwise you are wasting development time. Just write the simplest / cleanest code that you can.

Template Argument Deduction

Put simply, Template Argument Deduction is the ability of templated classes to determine the type of the passed arguments for constructors without explicitly stating the type.

Before C++17, to construct an instance of a templated class we had to explicitly state the types of the argument (or use one of the make_xyz support functions).

Here, p is an instance of the class pair and is initialized with values of 2 and 4.5. Or the other method of achieving this would be:

Specifying template arguments, as in:

should be unnecessary since they can be inferred from the type of the arguments – as is usual with template functions.

In C++17, this requirement for specifying the types for a templated class constructor has been abolished. This means that we can now write:

This is a much cleaner way of coding – and in this case we could even wrap it as:

There is more to it than that, and to dig deeper into that feature you can check out Simon Brand’s presentation about Template Argument Deduction.

Selection Initialization

Selection Initialization allows for optional variable initialization within if and switch statements – similar to that used within for statements. Consider:

Here the scope of a is limited to the for statement. But consider:

Here variable a is used only within the if statement but has to be defined outside within its own block if we want to limit its scope. But in C++17 this can be written as:

Which follows the same initialization syntax as the for statement – with the initialization part separated from the selection part by a semicolon ( ; ). This same initialization syntax can similarly be used with the switch statement. Consider:

Which all nicely helps C++ to be more concise, intuitive and correct! How many of us have written code such as:

Where a before the second if hasn’t been initialized properly before the test (an error) but isn’t picked up by the compiler because of the earlier definition – which is still in scope as it isn’t defined within its own block. If this had been coded in C++17 as:

Then this would have been picked up by the compiler and reported as an error. A compiler error costs much less to fix than an unknown run-time problem!

C++17 helps making code simpler

Template Argument Deduction allows us to avoid writing redundant template parameters and helper functions to deduce them. And Selection Initialization make the initialization in if and switch statements consistent with the one in for statements – and avoids the pitfall of variable scoping being too large.

Create a console calculator in C++

The usual starting point for a C++ programmer is a «Hello, world!» application that runs on the command line. That’s what you’ll create first in Visual Studio in this article, and then we’ll move on to something more challenging: a calculator app.

Prerequisites

Create your app project

Visual Studio uses projects to organize the code for an app, and solutions to organize your projects. A project contains all the options, configurations, and rules used to build your apps. It also manages the relationship between all the project’s files and any external files. To create your app, first, you’ll create a new project and solution.

If you’ve just started Visual Studio, you’ll see the Visual Studio Start dialog box. Choose Create a new project to get started.

Otherwise, on the menubar in Visual Studio, choose File > New > Project. The Create a new project window opens.

In the list of project templates, choose Console App, then choose Next.

Make sure you choose the C++ version of the Console App template. It has the C++, Windows, and Console tags, and the icon has «++» in the corner.

In the Configure your new project dialog box, select the Project name edit box, name your new project CalculatorTutorial, then choose Create.

An empty C++ Windows console application gets created. Console applications use a Windows console window to display output and accept user input. In Visual Studio, an editor window opens and shows the generated code:

Verify that your new app builds and runs

The template for a new Windows console application creates a simple C++ «Hello World» app. At this point, you can see how Visual Studio builds and runs the apps you create right from the IDE.

To build your project, choose Build Solution from the Build menu. The Output window shows the results of the build process.

To run the code, on the menu bar, choose Debug, Start without debugging.

Press a key to dismiss the console window and return to Visual Studio.

You now have the tools to build and run your app after every change, to verify that the code still works as you expect. Later, we’ll show you how to debug it if it doesn’t.

Edit the code

Now let’s turn the code in this template into a calculator app.

In the CalculatorTutorial.cpp file, edit the code to match this example:

To save the file, enter Ctrl+S, or choose the Save icon near the top of the IDE, the floppy disk icon in the toolbar under the menu bar.

To run the application, press Ctrl+F5 or go to the Debug menu and choose Start Without Debugging. You should see a console window appear that displays the text specified in the code.

Close the console window when you’re done.

Add code to do some math

It’s time to add some math logic.

To add a Calculator class

Go to the Project menu and choose Add Class. In the Class Name edit box, enter Calculator. Choose OK. Two new files get added to your project. To save all your changed files at once, press Ctrl+Shift+S. It’s a keyboard shortcut for File > Save All. There’s also a toolbar button for Save All, an icon of two floppy disks, found beside the Save button. In general, it’s good practice to do Save All frequently, so you don’t miss any files when you save.

You should now have three tabs open in the editor: CalculatorTutorial.cpp, Calculator.h, and Calculator.cpp. If you accidentally close one of them, you can reopen it by double-clicking it in the Solution Explorer window.

In Calculator.h, remove the Calculator(); and

Calculator(); lines that were generated, since you won’t need them here. Next, add the following line of code so the file now looks like this:

A pop-up appears that gives you a peek of the code change that was made in the other file. The code was added to Calculator.cpp.

Currently, it just returns 0.0. Let’s change that. Press Esc to close the pop-up.

Switch to the Calculator.cpp file in the editor window. Remove the Calculator() and

If you build and run the code again at this point, it will still exit after asking which operation to perform. Next, you’ll modify the main function to do some calculations.

To call the Calculator class member functions

Now let’s update the main function in CalculatorTutorial.cpp:

Build and test the code again

Now it’s time to test the program again to make sure everything works properly.

Press Ctrl+F5 to rebuild and start the app.

Debug the app

Since the user is free to type anything into the console window, let’s make sure the calculator handles some input as expected. Instead of running the program, let’s debug it instead, so we can inspect what it’s doing in detail, step-by-step.

To run the app in the debugger

Set a breakpoint on the result = c.Calculate(x, oper, y); line, just after the user was asked for input. To set the breakpoint, click next to the line in the gray vertical bar along the left edge of the editor window. A red dot appears.

Now when we debug the program, it always pauses execution at that line. We already have a rough idea that the program works for simple cases. Since we don’t want to pause execution every time, let’s make the breakpoint conditional.

Now we pause execution at the breakpoint specifically if a division by 0 is attempted.

Useful windows in the debugger

Whenever you debug your code, you may notice that some new windows appear. These windows can assist your debugging experience. Take a look at the Autos window. The Autos window shows you the current values of variables used at least three lines before and up to the current line. To see all of the variables from that function, switch to the Locals window. You can actually modify the values of these variables while debugging, to see what effect they would have on the program. In this case, we’ll leave them alone.

You can also just hover over variables in the code itself to see their current values where the execution is currently paused. Make sure the editor window is in focus by clicking on it first.

To continue debugging

Now that the point of execution is at the start of the Calculate function, press F10 to move to the next line in the program’s execution. F10 is also known as Step Over. You can use Step Over to move from line to line, without delving into the details of what is occurring in each part of the line. In general you should use Step Over instead of Step Into, unless you want to dive more deeply into code that is being called from elsewhere (as you did to reach the body of Calculate ).

Continue using F10 to Step Over each line until you get back to the main() function in the other file, and stop on the cout line.

This result happens because division by zero is undefined, so the program doesn’t have a numerical answer to the requested operation.

To fix the «divide by zero» error

Let’s handle division by zero more gracefully, so a user can understand the problem.

Make the following changes in CalculatorTutorial.cpp. (You can leave the program running as you edit, thanks to a debugger feature called Edit and Continue):

Now press F5 once. Program execution continues all the way until it has to pause to ask for user input. Enter 10 / 0 again. Now, a more helpful message is printed. The user is asked for more input, and the program continues executing normally.

When you edit code while in debugging mode, there is a risk of code becoming stale. This happens when the debugger is still running your old code, and has not yet updated it with your changes. The debugger pops up a dialog to inform you when this happens. Sometimes, you may need to press F5 to refresh the code being executed. In particular, if you make a change inside a function while the point of execution is inside that function, you’ll need to step out of the function, then back into it again to get the updated code. If that doesn’t work for some reason and you see an error message, you can stop debugging by clicking on the red square in the toolbar under the menus at the top of the IDE, then start debugging again by entering F5 or by choosing the green «play» arrow beside the stop button on the toolbar.

Understanding the Run and Debug shortcuts

Close the app

Add Git source control

Now that you’ve created an app, you might want to add it to a Git repository. We’ve got you covered. Visual Studio makes that process easy with Git tools you can use directly from the IDE.

To associate your code with Git, you start by creating a new Git repository where your code is located. Here’s how:

In the status bar at the bottom-right corner of Visual Studio, select Add to Source Control, and then select Git.

In the Create a Git repository dialog box, sign in to GitHub.

The repository name auto-populates based on your folder location. By default, your new repository is private, which means you’re the only one who can access it.

Select Create and Push.

After you create your repository, you see status details in the status bar.

The second icon with the pencil shows the number of uncommitted changes to your code. You can select this icon to view those changes in the Git Changes window.

To learn more about how to use Git with your app, see the Visual Studio version control documentation.

The finished app

Congratulations! You’ve completed the code for the calculator app, built and debugged it, and added it to a repo, all in Visual Studio.

Next steps

The usual starting point for a C++ programmer is a «Hello, world!» application that runs on the command line. That’s what you’ll create in Visual Studio in this article, and then we’ll move on to something more challenging: a calculator app.

Prerequisites

Create your app project

On the menubar in Visual Studio, choose File > New > Project. The New Project window opens.

On the left sidebar, make sure Visual C++ is selected. In the center, choose Windows Console Application.

In the Name edit box at the bottom, name the new project CalculatorTutorial, then choose OK.

Verify that your new app builds and runs

The template for a new windows console application creates a simple C++ «Hello World» app. At this point, you can see how Visual Studio builds and runs the apps you create right from the IDE.

To build your project, choose Build Solution from the Build menu. The Output window shows the results of the build process.

To run the code, on the menu bar, choose Debug, Start without debugging.

Press a key to dismiss the console window and return to Visual Studio.

You now have the tools to build and run your app after every change, to verify that the code still works as you expect. Later, we’ll show you how to debug it if it doesn’t.

Edit the code

Now let’s turn the code in this template into a calculator app.

In the CalculatorTutorial.cpp file, edit the code to match this example:

To save the file, enter Ctrl+S, or choose the Save icon near the top of the IDE, the floppy disk icon in the toolbar under the menu bar.

To run the application, press Ctrl+F5 or go to the Debug menu and choose Start Without Debugging. If you get a pop-up that says This project is out of date, you may select Do not show this dialog again, and then choose Yes to build your application. You should see a console window appear that displays the text specified in the code.

Close the console window when you’re done.

Add code to do some math

It’s time to add some math logic.

To add a Calculator class

In Calculator.h, remove the Calculator(); and

Calculator(); lines that were generated, since you won’t need them here. Next, add the following line of code so the file now looks like this:

Currently, it just returns 0.0. Let’s change that. Press Esc to close the pop-up.

Switch to the Calculator.cpp file in the editor window. Remove the Calculator() and

If you build and run the code again at this point, it will still exit after asking which operation to perform. Next, you’ll modify the main function to do some calculations.

To call the Calculator class member functions

Now let’s update the main function in CalculatorTutorial.cpp:

Build and test the code again

Now it’s time to test the program again to make sure everything works properly.

Press Ctrl+F5 to rebuild and start the app.

Debug the app

To run the app in the debugger

Now we pause execution at the breakpoint specifically if a division by 0 is attempted.

Useful windows in the debugger

To see all of the variables from that function, switch to the Locals window. You can actually modify the values of these variables while debugging, to see what effect they would have on the program. In this case, we’ll leave them alone.

You can also just hover over variables in the code itself to see their current values where the execution is currently paused. Make sure the editor window is in focus by clicking on it first.

To continue debugging

Continue using F10 to Step Over each line until you get back to the main() function in the other file, and stop on the cout line.

This result happens because division by zero is undefined, so the program doesn’t have a numerical answer to the requested operation.

To fix the «divide by zero» error

Let’s handle division by zero more gracefully, so a user can understand the problem.

Make the following changes in CalculatorTutorial.cpp. (You can leave the program running as you edit, thanks to a debugger feature called Edit and Continue):

Understanding the Run and Debug shortcuts

Close the app

Congratulations! You’ve completed the code for the calculator app, and built and debugged it in Visual Studio.

C++/CX Part 1 of [n]: A Simple Class

Visual CPP Team

In this article we’ll consider the basics of C++/CX by looking at a simple Windows Runtime class; we’ll skim over some of the details, but don’t worry: we’ll come back and cover them in future posts. The code in this post is complete, though some namespace qualification is omitted for brevity; attached to this article is a Visual Studio solution containing the complete code for both the C++/CX and the WRL component, along with a simple test app that uses both.

Alright. Here’s our simple class:

This is a rather silly class, but it is sufficient to demonstrate some of the fundamentals of both C++/CX and Windows Runtime. Aside from the public ref and sealed in the class declaration, this class looks exactly like an ordinary C++ class. This is a good thing: our C++/CX code should look similar to similar C++ code, but should be sufficiently different that we (and the compiler!) can identify it as being different.

So, what does it really mean that this class is a sealed, public, ref class? A ref class is a reference type. Windows Runtime is built atop COM, and a Windows Runtime reference type is effectively a COM class type. Whenever we interact with a reference type object, we do so indirectly (by reference), via a pointer to an interface that the reference type implements. Since we never interact with a reference type by value, its implementation is opaque: so long as its existing interface remains unchanged, its implementation may be modified without affecting other components that depend on it (new functionality can be added, but not removed).

A public type is visible outside of the component that defines it, and other components may refer to and use this type. Types can also be private (which is the default); a private type can only be referred to from within the component that defines it. The Windows Metadata file for a C++/CX component only contains metadata for public types. There are fewer restrictions on private types than on public types because private types do not appear in metadata and thus are not constrained by some of the rules of Windows Runtime.

The sealed simply specifies that this class may not be used as a base class. Most public Windows Runtime types are sealed (currently, the only public types that may be unsealed are those derived from Windows::UI::Xaml::DependencyObject ; these types are used by XAML apps).

The “Ref classes and structs (C++/CX)” page in the aforementioned Visual C++ Language Reference has a good roundup of other interesting facts about reference types.

Interfaces

I said above that whenever we interact with a reference type object, we do so via an interface that the reference type implements. You may have noticed that it looks like our Number class doesn’t implement any interfaces: it has no base class list at all. Thankfully, the compiler is going to help us out here so that our Number class isn’t useless.

The Number class is then transformed to declare this interface. If our class declared any new public virtual members (i.e., not overrides of base class virtual member functions) or any virtual or nonvirtual protected members, the compiler would generate interfaces for those as well.

Note that these automatically generated interfaces only declare members that aren’t already declared by an interface that the class explicitly implements. So, for example, if we declared another interface:

and defined our Number class as implementing this interface, the automatically generated __INumberPublicNonVirtuals would only define the SetValue member function.

Error Handling

In modern C++ code, exceptions are usually used for error reporting (not always, but they should be the default). A function is expected to return its result directly (as a return value) and throw an exception if a failure occurs. However, exceptions are not portable across different languages and runtimes; exception handling machinery varies quite a bit. Even within C++ code exceptions can be problematic, as different compilers may implement exceptions differently.

Since exceptions don’t work well across different languages, Windows Runtime does not use them; instead, each function returns an error code (an HRESULT) indicating success or failure. If a function needs to return a value, the value is returned via an out parameter. This is the same convention used by COM. It’s up to each language projection to translate between error codes and the natural error handling facility for that language.

The important thing is that both components–the C# component and the C++ component–get to handle errors naturally using exceptions, even though they use different exception handling machinery. We’ll cover the details of which exceptions get translated at the C++/CX boundary, and how the translation takes place, in a future article (this topic is sufficiently complex that it warrants separate treatment). For the moment, it is sufficient to know that the translation happens automatically.

Member Functions

We’ve intentionally made our Number class very simple: neither GetValue nor SetValue can throw, and a call to either will therefore always succeed. We can therefore use them to demonstrate how the compiler transforms our C++/CX member functions into the real ABI functions. GetValue is a bit more interesting since it returns a value, so let’s take a look at it:

The compiler will generate a new function with the correct ABI signature; for example,

We’ve named our wrapper function __abi_GetValue ; this is the name that the compiler gives to the function on the interface that it generates; in the class it uses a much longer name with lots of underscores to ensure that it doesn’t conflict with any user-declared functions or functions inherited from other classes or interfaces. The name of the function doesn’t matter at runtime, so it doesn’t really matter what name the function has. At runtime, functions are called via vtable lookup, and since the compiler is generating the wrapper functions, it knows which function pointers to place into the vtables.

A wrapper is generated for our SetValue function following the same pattern, with the exception that no out parameter is added because it returns no value.

A Simple Class, without C++/CX

With what we’ve discussed so far, we already have enough information to implement our Number class using C++ with the help of WRL and without using C++/CX.

When using C++/CX, the C++ compiler will generate both the Windows Metadata (WinMD) file for the component and the DLL that defines all of the types. When we don’t use C++/CX, we need to use IDL to define anything that needs to end up in metadata and use midlrt to generate a C++ header file and a Windows Metadata file from the IDL. For those experienced with COM, this should be quite familiar.

First, we need to define an interface for our Number type. This is equivalent to the __INumberPublicNonVirtuals interface that the compiler generated for us automatically when we were using C++/CX. Here, we’ll just name our interface INumber :

We also need to define the Number class itself in the IDL file, because it is public and therefore needs to end up in the metadata file:

The activatable attribute used here specifies that this class is default constructible. The details of how object construction works will be covered in a future article. For the moment, it’s sufficient to know that this activatable attribute will generate the required metadata in the metadata file to report the Number class as default constructible.

And, that’s all that is required in the IDL file. If you compare the WinMD file produced by this IDL file with the one produced for our C++/CX component, you’ll see that they are largely the same: the interface has a different name, and there are a few extra attributes applied to types in the C++/CX component, but they are otherwise the same.

The RuntimeClass class template and the InspectableClass macro are both from WRL: together they handle much of the mundane, repetitive work to implement a Windows Runtime class. The RuntimeClass class template takes as its arguments a set of interfaces that the class will implement and it provides a default implementation of the IInspectable interface member functions. The InspectableClass macro takes as its arguments the name of the class and the trust level of the class; these are required to implement pieces of the IInspectable interface.

Finally, because our Number type is default constructible, and because the default constructor is public, meaning that other components can create an instance of this class, we need to implement the logic required to enable other components to call the constructor of our class. This involves implementing a factory class and registering the factory so that we can return an instance of the factory when asked. There’s a fair bit of work required here, but since we only have a default constructor, we can simply use the ActivatableClass macro from WRL:

And, that’s it! The WRL component requires a bit more than three times as much code as the C++/CX component, but this is just a small, simple component. As things get more complex, and as we use more features of Windows Runtime, we’ll see that the WRL-based code both grows and becomes more complex much faster than the C++/CX-based code.

In our next post, we’ll discuss hats ( ^ ) in detail, and in future posts we’ll cover the details of construction, exception handling, and other interesting topics.

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Simple C++ code not working

This very simple code gives me tons of errors:

7 Answers 7

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Try using ‘g++’ instead of ‘gcc’.

To add to what others have said: g++ is the GNU C++ compiler. gcc is the GNU compiler collection (not the GNU C compiler, as many people assume). gcc serves as a frontend for g++ when compiling C++ sources. gcc can compile C, C++, Objective-C, Fortran, Ada, assembly, and others.

Additionally, you will have to add a return 0; at the end of your main() function.

if your compiler is picky you may want to add that all important return 0; at the end there

You declared your main() as returning an int yet you have no return statement. Add return 0; and see if that helps. If that doesn’t solve your problem, try editing your post to include some representative lines from those errors your getting and maybe we can help you better.

g++ was the right answer for me too, I voted it up, thanks.

But my code, a little ditty that I’ve been using since Feb 13, 1998 (first comment), to calculate effective gross pay and withholding for our kid’s nanny, was far TOO simple even for g++. In terms of the example above, my Stroustrup-second-edition-compliant dinosaur went:

This will give you a full terminal window of error messages. Everything except the curly braces is an error! AND its missing a return line. Time was, this would compile and run correctly in commercial C++ development environments.

Kicking it new-school, I’m now using: // just simple enough

The original questioner had the std::cout and used string from

«simple» is a relative term.

Not the answer you’re looking for? Browse other questions tagged c++ gcc g++ or ask your own question.

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Tutorial: Create a simple application with C#

By completing this tutorial, you’ll become familiar with many of the tools, dialog boxes, and designers that you can use when you develop applications with Visual Studio. You’ll create a «Hello, World» application, design the UI, add code, and debug errors, while you learn about working in the integrated development environment (IDE).

Prerequisites

Configure the IDE

When you launch Visual Studio, the start window opens first. Select Continue without code to open the development environment. You’ll see tool windows, the menus and toolbars, and the main window space. Tool windows are docked on the left and right sides of the application window. The search box, menu bar, and the standard toolbar are located at the top. When you load a solution or project, editors and designers appear in the central space of the application window. When you develop an application, you’ll spend most of your time in this central area.

Create the project

When you create an application in Visual Studio, you first create a project and a solution. For this example, you’ll create a Windows Presentation Foundation (WPF) project.

Open Visual Studio.

On the start window, choose Create new project.

On the Create a new project screen, search for «WPF,» choose WPF Application, and then choose Next.

At the next screen, give the project a name, HelloWPFApp, and choose Next.

In the Additional information window, .NET Core 3.1 should already be selected for your target framework. If not, select .NET Core 3.1. Then, choose Create.

Visual Studio creates the HelloWPFApp project and solution, and Solution Explorer shows the various files. The WPF Designer shows a design view and a XAML view of MainWindow.xaml in a split view. You can slide the splitter to show more or less of either view. You can choose to see only the visual view or only the XAML view.

For more information about XAML (eXtensible Application Markup Language), see the XAML overview for WPF page.

After you create the project, you can customize it. To do so, choose Properties Window from the View menu, or press F4. Then, you can display and change options for project items, controls, and other items in an application.

Open Visual Studio.

On the start window, choose Create a new project.

On the Create a new project screen, search for «WPF,» choose WPF Application, and then choose Next.

At the next screen, give the project a name, HelloWPFApp, and choose Next.

In the Additional information window, .NET 6.0 (Long-term support) should already be selected for your target framework. If not, select .NET 6.0 (Long-term support). Then, choose Create.

For more information about XAML (eXtensible Application Markup Language), see the XAML overview for WPF page.

Design the user interface (UI)

If the designer is not open, select MainWindow.xaml and press Shift+F7 to open the designer.

We’ll add three types of controls to this application: a TextBlock control, two RadioButton controls, and a Button control.

Add a TextBlock control

Press Ctrl+Q to activate the search box and type Toolbox. Choose View > Toolbox from the results list.

In the Toolbox, expand the Common WPF Controls node to see the TextBlock control.

Add a TextBlock control to the design surface by choosing the TextBlock item and dragging it to the window on the design surface. Center the control near the top of the window. In Visual Studio 2019 and later, you can use the red guidelines to center the control.

Your window should resemble the following illustration:

The XAML markup should look something like the following example:

Press Ctrl+Q to activate the search box and type Toolbox. Choose View > Toolbox from the results list.

In the Toolbox, expand the Common WPF Controls node to see the TextBlock control.

Add a TextBlock control to the design surface by choosing the TextBlock item and dragging it to the window on the design surface. Center the control near the top of the window. You can use the guidelines to center the control.

Your window should resemble the following image:

The XAML markup should look something like the following example:

Customize the text in the text block

In the XAML view, locate the markup for TextBlock and change the Text attribute from TextBox to Select a message option and then choose the Display button.

The XAML markup should look something like the following example:

Center the TextBlock again if you like, and then save your changes by pressing Ctrl+S or using the File menu item.

Next, you’ll add two RadioButton controls to the form.

Add radio buttons

In the Toolbox, find the RadioButton control.

Add two RadioButton controls to the design surface by choosing the RadioButton item and dragging it to the window on the design surface. Move the buttons (by selecting them and using the arrow keys) so that the buttons appear side by side under the TextBlock control. Use the red guidelines to align the controls.

Your window should look like this:

Next, you’ll add display text for each RadioButton control. The following procedure updates the Content property for a RadioButton control.

In the Toolbox, find the RadioButton control.

Your window should look like this:

Next, you’ll add display text for each RadioButton control. The following procedure updates the Content property for a RadioButton control.

Add display text for each radio button

Update the Content attribute for the HelloButton and GoodbyeButton to «Hello» and «Goodbye» in the XAML. The XAML markup should now look similar to the following example:

Set a radio button to be checked by default

In this step, we’ll set HelloButton to be checked by default so that one of the two radio buttons is always selected.

In the XAML view, locate the markup for HelloButton.

The XAML markup should now look similar to the following example:

The final UI element that you’ll add is a Button control.

Add the button control

In the Toolbox, find the Button control, and then add it to the design surface under the RadioButton controls by dragging it to the form in the design view. If you’re using Visual Studio 2019 or later, a red line helps you center the control.

Your window should resemble the following illustration.

The XAML markup should now look similar to the following example:

In the Toolbox, find the Button control, and then add it to the design surface under the RadioButton controls by dragging it to the form in the design view. The guidelines can help you center the control.

Your window should resemble the following screenshot.

The XAML markup should now look similar to the following example:

Add code to the display button

When this application runs, a message box appears after a user chooses a radio button and then chooses the Display button. One message box will appear for Hello, and another will appear for Goodbye. To create this behavior, you’ll add code to the Button_Click event in MainWindow.xaml.cs.

On the design surface, double-click the Display button.

MainWindow.xaml.cs opens, with the cursor in the Button_Click event.

Enter the following code:

Save the application.

On the design surface, double-click the Display button.

MainWindow.xaml.cs opens, with the cursor in the Button_Click event.

Enter the following code:

Save the application.

Debug and test the application

Next, you’ll debug the application to look for errors and test that both message boxes appear correctly. The following instructions tell you how to build and launch the debugger, but later you might read Build a WPF application (WPF) and Debug WPF for more information.

Change the name of MainWindow.xaml

Let’s give MainWindow a more specific name. In Solution Explorer, right-click on MainWindow.xaml and choose Rename. Rename the file to Greetings.xaml.

Find and fix errors

In this step, you’ll find the error that we caused earlier by changing the name of the MainWindow.xaml file.

Start debugging and find the error

Start the debugger by pressing F5 or selecting Debug, then Start Debugging.

A Break Mode window appears, and the Output window indicates that an IOException has occurred: Cannot locate resource ‘mainwindow.xaml’.

Stop the debugger by choosing Debug > Stop Debugging.

We renamed MainWindow.xaml to Greetings.xaml, but the code still refers to MainWindow.xaml as the startup URI for the application, so the project can’t start.

Start the debugger by pressing F5 or selecting Debug, then Start Debugging.

A Break Mode window appears, and the Output window indicates that an IOException has occurred: Cannot locate resource ‘mainwindow.xaml’.

Stop the debugger by choosing Debug > Stop Debugging.

We renamed MainWindow.xaml to Greetings.xaml at the start of this tutorial, but the code still refers to MainWindow.xaml as the startup URI for the application, so the project can’t start.

Specify Greetings.xaml as the startup URI

In Solution Explorer, open the App.xaml file.

As an optional step, it will avoid confusion to change the title of your application window to match this new name.

In Solution Explorer, open the Greetings.xaml file that you just renamed.

Start the debugger again (press F5). You should now see the Greetings window of your application.

Now close the application window to stop debugging.

Debug with breakpoints

You can test the code during debugging by adding some breakpoints. You can add breakpoints by choosing Debug > Toggle Breakpoint, by clicking in the left margin of the editor next to the line of code where you want the break to occur, or by pressing F9.

Add breakpoints

Open Greetings.xaml.cs, and select the following line: MessageBox.Show(«Hello.»)

Add a breakpoint from the menu by selecting Debug, then Toggle Breakpoint.

A red circle appears next to the line of code in the far left margin of the editor window.

Press the F9 key to add a breakpoint, and then press F5 to start debugging.

In the Greetings window, choose the Hello radio button, and then choose the Display button.

The line MessageBox.Show(«Hello.») is highlighted in yellow. At the bottom of the IDE, the Autos, Locals, and Watch windows are docked together on the left side, and the Call Stack, Breakpoints, Exception Settings, Command, Immediate, and Output windows are docked together on the right side.

On the menu bar, choose Debug > Step Out.

The application resumes execution, and a message box with the word «Hello» appears.

Choose the OK button on the message box to close it.

In the Greetings window, choose the Goodbye radio button, and then choose the Display button.

The line MessageBox.Show(«Goodbye.») is highlighted in yellow.

Choose the F5 key to continue debugging. When the message box appears, choose the OK button on the message box to close it.

Close the application window to stop debugging.

On the menu bar, choose Debug > Disable All Breakpoints.

Open Greetings.xaml.cs, and select the following line: MessageBox.Show(«Hello.»)

Add a breakpoint from the menu by selecting Debug, then Toggle Breakpoint.

A red circle appears next to the line of code in the far left margin of the editor window.

Press the F9 key to add a breakpoint, and then press F5 to start debugging.

In the Greetings window, choose the Hello radio button, and then choose the Display button.

On the menu bar, choose Debug > Step Out.

The application resumes execution, and a message box with the word «Hello» appears.

Choose the OK button on the message box to close it.

In the Greetings window, choose the Goodbye radio button, and then choose the Display button.

The line MessageBox.Show(«Goodbye.») is highlighted in yellow.

Choose the F5 key to continue debugging. When the message box appears, choose the OK button on the message box to close it.

Close the application window to stop debugging.

On the menu bar, choose Debug > Disable All Breakpoints.

View a representation of the UI elements

In the running app, you should see a widget that appears at the top of your window. The widget is a runtime helper that provides quick access to some helpful debugging features. Select the first button, Go to Live Visual Tree. You should see a window with a tree that contains all the visual elements of your page. Expand the nodes to find the buttons you added.

Build a release version of the application

Now that you’ve verified that everything works, you can prepare a release build of the application.

On the main menu, select Build > Clean solution to delete intermediate files and output files that were created during previous builds. This step isn’t required, but it cleans up the debug build outputs.

Change the build configuration for HelloWPFApp from Debug to Release by using the dropdown control on the toolbar (it says «Debug» currently).

Build the solution by choosing Build > Build Solution.

Congratulations on completing this tutorial! You can find the .exe you built under your solution and project directory (. \HelloWPFApp\HelloWPFApp\bin\Release).

Next steps

Congratulations on completing this tutorial! To learn even more, continue with the following tutorials.

10 главных конструкций языка C

Простое введение в сложный язык.

Быстрый обзор основных конструкций языка C для тех, кто хочет разобраться в основах. Здесь вы встретите много очевидных и понятных конструкций, которые есть во многих языках, — это потому, что многие языки взяли эти конструкции как раз из языка C.

На самом деле в статье их 11, но 10 звучит лучше.

👉 Точка с запятой ставится после каждой команды.

Переменные и типы данных

Чтобы объявить переменную в C, нужно сначала указать её тип, а потом написать имя. Отдельного служебного слова для создания переменной в C нет.

В C есть разделение на короткие (short), обычные и длинные (long) переменные — на 2, 4 и 8 байт соответственно. Это нужно для экономии памяти, чтобы выделять ровно то количество байт, которое нужно для работы программы.

Внешние файлы и директивы

Чтобы программа получила некоторые дополнительные возможности, которых нет в коде по умолчанию, используют директивы. Они обычно пишутся в начале программы и начинаются с символа решётки:

Формат программы

В каждой программе на C должна быть функция main(), внутри которой размещается основной код. Большинство компиляторов требуют, чтобы мы указали тип этой функции — обычно можно использовать int (целочисленный) или void (пустой). Все остальные функции добавляются по желанию, но main() должна быть всегда.

Ввод и вывод

Для вывода используется команда printf():

Если нужен ввод данных, то используют команду scanf():

Присваивание и сравнение

C использует классический подход:

один символ «равно» — присваивание

два символа «равно» — сравнение

Остальные операторы сравнения и логические операторы такие же, как и в других языках. Каждое сравнение берётся в скобки.

Условный оператор if

Тоже всё стандартно (потому что C во многом этот стандарт и создал):

if (условие) <
/* если условие верно, делаем что-то */
> else <
/* если условие неверно, делаем что-то другое */
>

Если блок с else не нужен, его можно не писать — короткий if тоже работает.

Оператор множественного выбора switch

Чтобы не плодить множество операторов if, когда нужно выбрать одно из нескольких значений, используют оператор switch:

Если не ставить команду break, то оператор будет продолжать выполнять остальные проверки, даже если найдёт совпадение по условию.

Цикл с предусловием for

Классический цикл, который в таком же виде используется во многих языках:

Особенность этого цикла в C в том, что он может работать и с дробными числами, например, увеличивать счётчик каждый раз на 0,1:

Циклы while и do-while

Если вы заранее не знаете, сколько раз будет выполняться цикл, используйте while или do-while. Первый проверяет условия до начала цикла (и если там истина — выполняет его), а второй делает проверку в самом конце.

В отличие от цикла for здесь программист сам должен следить за тем, чтобы цикл когда-нибудь прекратился. Если забыть изменить в теле цикла переменную, от которой зависит условие, то программа может зациклиться и зависнуть.

Функции

В языке C программист может объявить сколько угодно функций. Каждая функция объявляется так:

тип_результата название (аргументы) <
тело_функции
>

Если у функции нет аргументов, то ставят просто две скобки, а если есть, то нужно обязательно указать их тип:

Классы, объекты и методы

В языке C такого нет. Если нужно ООП — используйте С++, про него будет в следующий раз.

Где лучше изучать C++?

Здравствуйте, на данный момент я являюсь самоучкой. Смотрю видео на Ютубе про изучение С++. Автор который меня учит «SimpleCode».

Он все хорошо рассказывает для чайников вроде меня.

Я хотел бы узнать. если ещё варианты изучения С++? Платные книги или бесплатные книги, курсы, видео или что-нибудь ещё.

Простой 2 комментария

Здравствуйте, я начинающий программист. Мой первый язык будет С++.
В процессе обучения я время от времени забываю синтаксис кода. Если быть точнее, то забываю часть кода.

И в процессе обучения бывает забываю некоторые моменты. Допустим я полностью изучил for, но while и do while я не пользуюсь, поэтому я частично забыл его синтаксис.

Я хотел бы узнать. если ещё варианты изучения С++? Платные книги или бесплатные книги, курсы, видео или что-нибудь ещё.

Я там предыдущие вопросы глянул ваши, в целом нормально, что вы что-то забываете, если не пользуетесь это обычное дело. Такие вещи вы рано или поздно запомните, либо можете просто написать простую программу с использованием конструкции и посматривать туда, если что-то забыли. Все вы не запомните.
Да тысячи этих книг, но обычно roadmap(можете погуглить c++ developer roadmap) выглядит примерно так:
1) изучение основ языка(циклы, понятие об ООП в с++, простая работа с указателями и памяться)
2) потом имеет смысл смотреть в сторону stl
3) изучаете qt, boost или что будет нужно

В целом для вуза скорее всего хватит simple code, если нет, то почитайте еще ravesly.
Ну а если нужен более/менее детальный ответ, то стоит написать для чего нужен язык, если нужен для пар вузе то любой книжки для новичков стр на 600 вам хватит скорее всего. Если работать с ним хотите, то охват слишком большой и нужно уточнять где хотите работать.

Simple code completion sample in Roslyn

I’d like to get started with code completion in Roslyn but could not find any simple examples that show how to do code completion.

2 Answers 2

Trending sort

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Switch to Trending sort

Roslyn does provide code completion services through the ICompletionService and ICompletionProvider interfaces, but they seem to mostly be internal and meant to be accessed when hosted within Visual Studio. However, it is possible to get a hold of the C# code completion types using a couple of reflection hacks, as illustrated by the ScriptCS Pad project. If you can get this to work, I expect you should get VS-grade code completion.

Alternatively, you can do it «by hand», using the public APIs provided by Roslyn. I am not well-versed in them, but the following should get you started in listing the members of the expression to the left of the member access dot. Note that it ignores extension methods and visibility rules, does no error handling and is probably flawed in many other ways. Doing this reliably probably doesn’t qualify as «simple» code completion, though.

EDIT: Note that this answer was probably made obsolete by the new Roslyn bits.

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A tour of the C# language

C# is an object-oriented, component-oriented programming language. C# provides language constructs to directly support these concepts, making C# a natural language in which to create and use software components. Since its origin, C# has added features to support new workloads and emerging software design practices. At its core, C# is an object-oriented language. You define types and their behavior.

C# emphasizes versioning to ensure programs and libraries can evolve over time in a compatible manner. Aspects of C#’s design that were directly influenced by versioning considerations include the separate virtual and override modifiers, the rules for method overload resolution, and support for explicit interface member declarations.

.NET architecture

Source code written in C# is compiled into an intermediate language (IL) that conforms to the CLI specification. The IL code and resources, such as bitmaps and strings, are stored in an assembly, typically with an extension of .dll. An assembly contains a manifest that provides information about the assembly’s types, version, and culture.

When the C# program is executed, the assembly is loaded into the CLR. The CLR performs Just-In-Time (JIT) compilation to convert the IL code to native machine instructions. The CLR provides other services related to automatic garbage collection, exception handling, and resource management. Code that’s executed by the CLR is sometimes referred to as «managed code.» «Unmanaged code,» is compiled into native machine language that targets a specific platform.

Hello world

The «Hello, World» program is traditionally used to introduce a programming language. Here it is in C#:

The output of the program is produced by the WriteLine method of the Console class in the System namespace. This class is provided by the standard class libraries, which, by default, are automatically referenced by the compiler.

Types and variables

A type defines the structure and behavior of any data in C#. The declaration of a type may include its members, base type, interfaces it implements, and operations permitted for that type. A variable is a label that refers to an instance of a specific type.

There are two kinds of types in C#: value types and reference types. Variables of value types directly contain their data. Variables of reference types store references to their data, the latter being known as objects. With reference types, it’s possible for two variables to reference the same object and possible for operations on one variable to affect the object referenced by the other variable. With value types, the variables each have their own copy of the data, and it isn’t possible for operations on one to affect the other (except for ref and out parameter variables).

C#’s value types are further divided into simple types, enum types, struct types, nullable value types, and tuple value types. C#’s reference types are further divided into class types, interface types, array types, and delegate types.

The following outline provides an overview of C#’s type system.

When a value of a value type is assigned to an object reference, a «box» is allocated to hold the value. That box is an instance of a reference type, and the value is copied into that box. Conversely, when an object reference is cast to a value type, a check is made that the referenced object is a box of the correct value type. If the check succeeds, the value in the box is copied to the value type.

There are several kinds of variables in C#, including fields, array elements, local variables, and parameters. Variables represent storage locations. Every variable has a type that determines what values can be stored in the variable, as shown below.

Program structure

As a small example, consider an assembly that contains the following code:

Because an assembly is a self-describing unit of functionality containing both code and metadata, there’s no need for #include directives and header files in C#. The public types and members contained in a particular assembly are made available in a C# program simply by referencing that assembly when compiling the program. For example, this program uses the Acme.Collections.Stack class from the acme.dll assembly:

To compile this program, you would need to reference the assembly containing the stack class defined in the earlier example.

C# programs can be stored in several source files. When a C# program is compiled, all of the source files are processed together, and the source files can freely reference each other. Conceptually, it’s as if all the source files were concatenated into one large file before being processed. Forward declarations are never needed in C# because, with few exceptions, declaration order is insignificant. C# doesn’t limit a source file to declaring only one public type nor does it require the name of the source file to match a type declared in the source file.

Further articles in this tour explain these organizational blocks.

How to: Run a C# program in Visual Studio

How to run a program depends on what you start from, the type of program, and whether you want to run under the debugger. In the simplest case, to build and run an open project in Visual Studio:

Start from a project

You can run a C# project or .csproj file if it’s a runnable program. If the project contains a C# file with a Main method, and its output is an executable or .exe file, it will probably run if it builds successfully.

If your program code is already in a Visual Studio project, open the project. To do so, you can double-click or tap on the .csproj file in Windows File Explorer, or choose Open a project in Visual Studio, browse to find the .csproj file, and select the file.

After the project loads in Visual Studio, if your Visual Studio solution has more than one project, make sure to set the project with the Main method as the startup project. To set the startup project, right-click on the project name or node in Solution Explorer and choose Set as Startup Project from the context menu.

To run the program, press Ctrl+F5, select Debug > Start without debugging from the top menu, or select the green Start button.

Visual Studio tries to build and run your project. At the bottom of the Visual Studio screen, the build output appears in the Output window, and any build errors appear in the Error List window.

If the build succeeds, the app runs as appropriate for the type of project. Console apps run in a terminal window, Windows desktop apps start in a new desktop window, and web apps run in a browser hosted by IIS Express.

Start from code

If you start from a code listing, code file, or small number of files, first make sure the code is a runnable program from a trusted source. Any app with a Main method is probably a runnable program. You can use the Console Application template to create a project to work with the app in Visual Studio.

Code listing for a single file

Several code listings or files on disk

Several files in a folder

If you have a folder with many files, first check for a project or solution file. Programs that Visual Studio creates have project and solution files. In Windows File Explorer, look for files with the .csproj or .sln extension. Double-click the .csproj file to open it in Visual Studio. See Start from a Visual Studio solution or project.

If the code is from another development environment, there’s no project file. Open the folder by choosing Open > Folder in Visual Studio. See Develop code without projects or solutions.

Start from a GitHub or Azure DevOps repo

If the code you want to run is in a GitHub or Azure DevOps repo, you can use Visual Studio to open the project directly from the repo. See Open a project from a repo.

Run the program

To start building the program, press the green Start button on the Visual Studio toolbar, or press F5 or Ctrl+F5. Using the Start button or F5 runs the program under the debugger.

Visual Studio attempts to build and run the code in your project. If a build doesn’t succeed, see the following sections for some ideas on how to get the project to build successfully.

Troubleshooting

Add references

To build properly, the code must be correct and have the right references to libraries or other dependencies. Red squiggly underlines in code or entries in the Error List show errors even before you compile and run the program. If the errors relate to unresolved names, you probably need to add a reference or a using directive, or both. If the code references any missing assemblies or NuGet packages, you need to add those references to the project.

Visual Studio tries to help you identify missing references. When a name is unresolved, a light bulb icon appears in the editor. Select the light bulb to see suggestions on how to fix the issue. Fixes might be to:

Add a using directive

Here’s an example of a missing using directive. You can add using System; to the start of the code file to resolve the unresolved name Console :

Add an assembly reference

.NET references can be assemblies or NuGet packages. In source code, the publisher or author usually explains what assemblies the code requires and what packages it depends on. To add a reference to a project manually, right-click the References node in Solution Explorer and choose Add Reference. In the Reference Manager, locate and add the required assembly.

You can find assemblies and add references by following the instructions in Add or remove references by using the Reference Manager.

Add a NuGet package

If Visual Studio detects a missing NuGet package, a light bulb appears and gives you the option to install the package:

If that doesn’t solve the issue or Visual Studio can’t locate the package, try searching for the package online. See Install and use a NuGet package in Visual Studio.

First program: a simple calculator

I’m reading this very good book, C# Player’s Guide, to learn C#. I then plan to make video games with Unity 3D after.

In one of the chapters, he asks us to make a (really) simple calculator as a console application using the switch statement:

The program that we’ll make is going to be a simple calculator. We’re going to ask the user to type in two numbers and then type in a math operation to perform on the two numbers.

Use a switch statement to handle the different operations in different ways. Allow the user to type in ’+’ for addition, ’-’ for subtraction, ’*’ for multiplication, ’/’ for division, and ’%’ for remainder.

What do you think of my first program? Is it well-formatted and well-written?

2 Answers 2

First of all you are not verifying the input of your program. You also don’t need the strings stringFirstNumber stringSecondNumber you can just put this all into a method that will check if the input is in correct format and also return the value something like this :

and use it like this :

Now, about the operations.. I’m not sure if you wanted the sign % to work as percentage because if that’s the case it wont. This is called modulus you can read more about it here https://msdn.microsoft.com/en-us/library/0w4e0fzs.aspx if you want to have percentages you must implement this yourself. Anyway I would recommend creating an array of strings that holds all your currently available operations and store them there something like this :

private means we are keeping this variable only in our current class (Program)

static means we are having just 1 instance of this variable.

readonly means we wont modify those variables it’s similar to const but it gives us a little bit more flexibility of where we can declare the value of the variable.

If the modifiers confuse you just remove them :

You need the static one since we are using this variable in static methods.

Let’s move on. Once we have our operations declared in a string array we can easily check if the user is entering a correct input by creating the following function :

Well we have the checker method which uses LINQ.Contains() this extension checks if a specific collection contains a specific value. Now we just need a method that will return a string value to our stringOperation

and use like this

Now notice that we are using only string’s. I removed the integer idea that you had initially. You can still implement it pretty easily working around with the indexes of the string array, but I don’t this is necessary. Also one thing to mention is that we are again taking a parameter in our method SetOperation well we could’ve avoided that since we have just 1 operation to be entered so we could’ve just do

I prefer the switch case version here because it’s more readable but you can go with if statements too

Notice that we don’t have else/default at the end in case of wrong input, because we already made sure the nasty user wont be able to proceed unless he sticks to our rules.

And lastly I edited this line

into a formated string which also looks a lot more readable :

Here’s the full code if you got confused where to put something :

Simple calculator in C

I made a very simple calculator in C that allows the user to perform calculations like addition, subtraction, multiplication and division. This is my first C program that I’ve made outside of my University course. It would be great to get some feedback on this program so that I can avoid bad practices early on in my coding.

5 Answers 5

I must say, I respectively disagree with @ishyfishy’s example of the addition function. Although, I do agree with the point about splitting the arithmetic functions away from the main function.

I believe that the arithmetic functions should only handle performing the arithmetic; all the I/O should be handled by main function (I have been taught that this is a good practice, although I do not have a source right now).

So, the «1» (addition) section of the switch statement in main would look something like this:

And the addition function simply looks like this:

This doesn’t make a much of a difference, but it speeds up your code a little bit.

For example, the end of the «1» (addition) section of the switch statement would look like this:

This is faster because it reduces memory interaction(however, not by much).

In this section:

You make 5 calls to the printf function when you could easily just put all the strings into one and split them up by newline in a single printf call:

This is also faster as you don’t have to call a function 5 times.

Only use printf when you are need to use the formatting feature. Other than that, you are over-complicating things.

If you merely need to output a string with a newline here or there, use the built-in puts function; it automatically outputs a string with a newline on the end (and you can add more if needed).

For example, this line:

I would give the user a chance to correct typing errors instead of just dumping them out of the program. Something like this, maybe:

You should check for the possibility of the user entering zero for the denominator in the division case, and print a warning. Something like this:

I dislike repeated code, and you have a lot of it. I would rewrite the switch statement something like what is shown below.

If you really want the operator in the output line, you can used a variable to hold this and set it in each branch of the switch statement.

I would allow the user to jump back to the beginning if they wanted. I would do this something like this:

Just a note, notice that I chanced the menu choice from an integer to a character so I could accept both numeric and character values. Also look at the conditional I used: if((choice ‘4’)) this is based on the knowledge that the ASCII character code for the digits are consecutive and run from 0x30 to 0x39, so I can test for a valid input by determining if the character codes are in this range. This probably is not portable to systems using other encoding than ASCII.

In the second example, you create and destroy result each function call.

Consider asking the user if they would like to return to the menu, in case they want to do multiple calculations.

You don’t need multiple printf statements for the menu options. Simply continuing as such is needed:

printf(«1. Addition\n2. Subtraction\n3. Multiplication\n4. Division\n\n»);

For example, a piece of your code:

This is done so that scanf does not go on reading the same invalid data ( when user enters characters or other invalid data) again and again and the loop from turning into an infinite loop.

The last line prints the error message and prompts the user to enter valid data.

You can use the same technique for the other scanf s in your code too.

Writing code in C? Simplify your life with sim-C

If you are working with C or have ever worked with C, then you know how frustrating it can get writing those long and (sometimes) complicated syntaxes, and how time-consuming it can get to debug a code just because of something as simple as a misplaced semicolon. While we wholeheartedly believe that C is one of the most powerful and impactful languages ever created, it sometimes can be tough for non-programmers. In this article, we will tell you about sim-C, a tool that aims to help you simplify your life.

sim-C?

In simple terms, sim-C is a tool that adds a layer of abstraction over the syntax of C, i.e it offers its users to write code in its own syntax and then converts that simple code into C code.

We know some of you will be concerned about your code slowing down as a result of using sim-C, but we assure you that the runtime of your code will not be affected due to it. This is because sim-C’s job is to convert code written in it’s high-level syntax to the syntax of C, hence only affecting the compilation time.

What do I need to know to use sim-C?

If you can write a = b + c in any programming language, you probably have more than sufficient knowledge to get started with sim-C. Since sim-C’s ultimate goal is to convert its simple concise code to C code, we recommend that you have a basic knowledge of the C language, but as we mentioned earlier, it is not a necessity by any means.

What does sim-C have to offer?

sim-C offers a very concise and simple syntax to the users. With sim-C you will surely be able to bring down your time of development. But perhaps the salient feature of sim-C is the ability to infer the datatypes of variables, that means you don’t have to worry about declaring integers/floats/doubles/chars etc, you can simply type ‘var name’ leaving the rest to sim-C.

sim-C is still in development phase (we released v0.1 alpha recently) and we are still adding new features regularly, so even if it is not for you right now, do keep an eye on it.

Final Words

While sim-C is far from being complete, we would really appreciate it if you were to check it out. Do let us know if you have any suggestions for us. Looking forward to hearing back from you.

Do check out our next post, Getting started with sim-C, to know how to install sim-C and run it.

sim-C is still in continuous development and some amazing changes are on the way!! Do check out the Github repo and star it to be in touch with the updates taking place.

Simple C# console Tic Tac Toe program

I’ve been teaching myself how to program for a little bit now, and was hoping to get some critique on my most recent project, creating a Tic Tac Toe program! I’m hoping for people to point out some of the flaws within my code, and some areas in which I should try to improve on going forward.

8 Answers 8

I’m using VisualStudio with Resharper Installed. This causes a big chunk of your code to grey out.

This is because the winFlag can’t be false. This because the loop above only exits when the winFlag is true.

So. there is a problem in there. We will get to that. Let’s do some cleanup.

CheckWin is a good place to start. Lots of verbosity. The need to add comments shows the method doesn’t speak by itself.

This pattern repeats. what is it doing? Checking for a line. Lets add a method for that.

Okay, nice, but there is another chunk of duplication. All the tests get done twice, once with ‘O’ and once with ‘X’. Lets deal with that. now we can do this in a couple of ways. Loop over possible pieces, or just change the IsLine to check all the pieces in the line match.

Lets try the second.

Now. what about all those «return true» exits from this method. We just need to return true if any of those cases are true.

Now. Interestingly Horizontal lines are all (x,x+1,x+2) and all vertical are (x,x+3,x+6). One diagonal is «(x, x+4, x+8)» the other is (3, 3+2, 3+4)

OK we could do more here. but I think this is enough.

Let’s look at the main logic.

Now that is one big function.

Lets break out some helper functions. Every time you have a comments I’ll make it a function. Same with the body of a loop.. make it a function.

That makes the first few lines.

Nice. I wonder if a player array is useful? maybe. but lets limit the changes for now and keep using the player variables.

In C++ it was good practice to have all your variables declared at the start of the method. In C# we move them to where they are first used. Try for the smallest scope you can for each variable. With that in mind it’s also a bad idea to reuse variables. Better to make a new one each time you need it. This decouples code that shouldn’t be coupled. This makes changing your code easier.

The ‘choice’ variable is reused each time we ask the user for data. Same with ‘correctInput’.

It’s always the same code, so let’s make a function.

The method is still too big to read. lets pull out «Checks to see if spot is taken already»

«What would you like to do now?»

I did do some code manipulation here. but now it’s a method that returns true to keep playing and false otherwise.

There are two turns and different logic for each. If we extract a method for the loop, we can see what parameters it needs

Lets look at «TakeTurn».

The only times ‘score1’ and ‘score2’ are used is the first few lines. Lets pull those out

Right.. lets group the ‘turn==1’ logic.

Pull out the method

This seems a lot like it should be inside TryToPlacePiece.

Now Main is readable. kinda 🙂

At this point it’s obvious why we are having problem with WinFlag.

‘CheckWin’ is setting the ‘winFlag’. But CheckWin doesn’t detect a draw. A draw is reached when there are no more places to put a piece. (or after 9 moves)

‘TryToPlaceAPiece’ also has a problem. It stops you putting a piece on-top of an opponents piece, but not on-top of your own.

The biggest smell left if this ‘turn’ variable. A lot of things are using it as their indicator as to which player is active. Why does the rest of the code care which player is active? The logic should be the same for both. Lets group together all the player specific logic. I’ll start by moving it all out of the main method and into helper methods.

We can use the players array, and I’ll make a score array and put the pieces into an array. then we get

These helpful methods.

OK This is getting way too long. lets jump some steps.

This is what Main looks like now. We are using ‘turn-1’ as a player index in the player array, scores array and pieces array. We might as well change turn to be 0 based, to remove the logic.

So. here is the final code. in total

The goal here was to make the code more readable. You want to go from «not obviously wrong» to «Obviously not wrong». Having small methods that show your intent and encapsulate your implementation decisions does this for you.

So. using the squint test again. The biggest method is somewhat manageable.

Taking this further.

C# is Object Oriented. You can use these features to separate the code into blocks each with it’s own single responsibility.

Some examples: a Board Object that knows how to draw itself and detect lines. A Player object that knows it’s score, name and what piece it is using. A Game object that knows the flow of a game. A Tournament object that knows how to start new games if people want to keep playing.

We can give that a go if you want more feedback.

The same player can place its sign on a allready taken (by him) place. You have defended against this for the opponent although you use inappropriate language here.

You should just check if the place in the grid is allready taken without checking who is currently playing.

I would suggest using a method for this like

now you can do the check by

or if you would introduce a small dictionary containing the O and X like

would become this

First of all, why pos has 10 elements and everywhere you counting from 1 to 9? Let this array to have 9 elements and count from 0.

You must rewrite the CheckWin method.

Define a list of all winning positions:

Then CheckWin will be (using LINQ and lambdas)

You don’t need to write boolean literals in conditions. Instead of

Your «DrawBoard» method could be improved.

Both » <0>| <1>| <2>» and «——————-» is repeated multiple times, so they can and should be stored in a variable to be more manageable. I understand this is a small project, but your current usage is a bad habit.

With this change, if you want to change the look of your board (For example add a «+» in the separator when it lines up with a «|», you only need to do it once.

Now, with this new code you can also clearly see that there’s a pattern between format and separator in your DrawBoard method. You could make this more flexible by using a For loop to create the board.

While the previous state looks nice for your current situation, the values i+X are hard coded and not flexible. To remedy this, you can send an Array to the WriteLine function to take parameters.

We’re almost done! As you have probably noticed, the format can be automated.

With these changes, you can probably see that your board could scale to a different format, such as a 5×5 sized board if you chose to do so with minimal changes. This added flexibility could prove to be useful in different scenarios, or if you decide to add different board formats. It is a much easier change and less prone human errors when you modify it.

I liked Maxim’s way of checking the winning state of the game so here is my take on it (starting from OP’s code, I have also added some coloring):

Here are some reasons I wrote it this way:

You have some good instincts.

Code should tell you 3 things: * What it’s doing. * How it’s doing it. * Why it’s doing it.

You address these things using different constructs in code.

When learning to code all code examples use comments to explain «what is happening» this is bad practice. Whenever you feel the need for a comment, that is good feedback. Write the comment, then say «is this a what? a how? or a why?»

Check your code. Most of these comments are marking out where a new method should be. 🙂 Try it!

First thing that jumps out at me is that you assume that the Players enter a number. Never trust users. What seems logical to you is not always what a User will think. Int.Parse will throw an exception if the string handed to it is not actually a number. I would change the following code:

I would change it to something like this:

First, removing the continue. It does nothing, since the loop will just continue anyway without it. Continue should only be used at the beginning or the middle of a loop, never the end.

Next is the try catch. In the event that the int.Parse fails because the user entered an incorrect string, either maliciously or because of fat fingers, then this will prevent the program from crashing because of uncaught exceptions.

Finally, I recommend breaking down the Main function, mostly for readability and comprehension. A good benchmark is that if you have a function that is over 100 lines long, then it should probably be split up into smaller functions. The code for playing a game should not really be in the same function as the victory text. Splitting the game itself into its own function would improve the readability, especially if you wish to return and read the code at a much later date.

Get code out of Program.cs and main

Now in Program.cs in you’ll need to make an instance of your GameGraphic to make use of it. But before we do, I want to introduce you to another type of class. A test class.

Unit tests

There are many different TestFrameworks available so you can search for them on your own (NUnit, xUnit, msTest. etc etc). Even though I’m part of the NUnit team I’ll recommend sticking with what is built into Visual Studio so that you don’t have to learn about NuGet and all that it brings to the table (although it is also a good easy research project). So you’ve created a new Test Project (Create Unit Test Project how to). Now lets write a test for GameGrahpics. But wait! It doesn’t compile! And even if it did it doesn’t lend it self to a easy test. Grumble.. ok not a huge problem. Really we only have 1 test that we need to write, we could write more and with any thing it takes practice, but I’m going to write my test to make GameGraphics work the way I want it to. So here it is:

I’ll leave it to you to make that test pass. If you get stuck there is a big hint in the UnitTest shown above. What i love about unit tests is that they are fast and tell you very easily if all your tests pass. Example your test should say this if you run it:

Notice how fast it ran? Test Duration: 0:00:00.0339269

Once you get that test to pass you’ll be able to create a new instance in your main method of GameGraphics and replace all calls to DrawBoard with your newly tested method. A quick note about static: I made a new instance of GameGraphics and made the DrawBoard NON-static. I did that because when you have many static methods in a class it is a good way checking if a new class can be made. Classes can be simple (and should be). When you see that you should ask your self if it should be responsible for ________?

Since its creation, C++ has become one of the most widely used programming languages in the world. Well-written C++ programs are fast and efficient. The language is more flexible than other languages: It can work at the highest levels of abstraction, and down at the level of the silicon. C++ supplies highly optimized standard libraries. It enables access to low-level hardware features, to maximize speed and minimize memory requirements. C++ can create almost any kind of program: Games, device drivers, HPC, cloud, desktop, embedded, and mobile apps, and much more. Even libraries and compilers for other programming languages get written in C++.

One of the original requirements for C++ was backward compatibility with the C language. As a result, C++ has always permitted C-style programming, with raw pointers, arrays, null-terminated character strings, and other features. They may enable great performance, but can also spawn bugs and complexity. The evolution of C++ has emphasized features that greatly reduce the need to use C-style idioms. The old C-programming facilities are still there when you need them. However, in modern C++ code you should need them less and less. Modern C++ code is simpler, safer, more elegant, and still as fast as ever.

The following sections provide an overview of the main features of modern C++. Unless noted otherwise, the features listed here are available in C++11 and later. In the Microsoft C++ compiler, you can set the /std compiler option to specify which version of the standard to use for your project.

Resources and smart pointers

Whenever possible, use a smart pointer to manage heap memory. If you must use the new and delete operators explicitly, follow the principle of RAII. For more information, see Object lifetime and resource management (RAII).

std::string and std::string_view

std::vector and other Standard Library containers

The standard library containers all follow the principle of RAII. They provide iterators for safe traversal of elements. And, they’re highly optimized for performance and have been thoroughly tested for correctness. By using these containers, you eliminate the potential for bugs or inefficiencies that might be introduced in custom data structures. Instead of raw arrays, use vector as a sequential container in C++.

When performance optimization is needed, consider using:

The array type when embedding is important, for example, as a class member.

DonвЂ™t use C-style arrays. For older APIs that need direct access to the data, use accessor methods such as f(vec.data(), vec.size()); instead. For more information about containers, see C++ Standard Library Containers.

Standard Library algorithms

Before you assume that you need to write a custom algorithm for your program, first review the C++ Standard Library algorithms. The Standard Library contains an ever-growing assortment of algorithms for many common operations such as searching, sorting, filtering, and randomizing. The math library is extensive. In C++17 and later, parallel versions of many algorithms are provided.

Here are some important examples:

To write a comparator, use strict and use named lambdas when you can.

auto instead of explicit type names

C++11 introduced the auto keyword for use in variable, function, and template declarations. auto tells the compiler to deduce the type of the object so that you don’t have to type it explicitly. auto is especially useful when the deduced type is a nested template:

Range-based for loops

C-style iteration over arrays and containers is prone to indexing errors and is also tedious to type. To eliminate these errors, and make your code more readable, use range-based for loops with both Standard Library containers and raw arrays. For more information, see Range-based for statement.

constexpr expressions instead of macros

Macros in C and C++ are tokens that are processed by the preprocessor before compilation. Each instance of a macro token is replaced with its defined value or expression before the file is compiled. Macros are commonly used in C-style programming to define compile-time constant values. However, macros are error-prone and difficult to debug. In modern C++, you should prefer constexpr variables for compile-time constants:

Uniform initialization

Move semantics

Modern C++ provides move semantics, which make it possible to eliminate unnecessary memory copies. In earlier versions of the language, copies were unavoidable in certain situations. A move operation transfers ownership of a resource from one object to the next without making a copy. Some classes own resources such as heap memory, file handles, and so on. When you implement a resource-owning class, you can define a move constructor and move assignment operator for it. The compiler chooses these special members during overload resolution in situations where a copy isn’t needed. The Standard Library container types invoke the move constructor on objects if one is defined. For more information, see Move Constructors and Move Assignment Operators (C++).

Lambda expressions

In C-style programming, a function can be passed to another function by using a function pointer. Function pointers are inconvenient to maintain and understand. The function they refer to may be defined elsewhere in the source code, far away from the point at which it’s invoked. Also, they’re not type-safe. Modern C++ provides function objects, classes that override the operator() operator, which enables them to be called like a function. The most convenient way to create function objects is with inline lambda expressions. The following example shows how to use a lambda expression to pass a function object, that the find_if function will invoke on each element in the vector:

Exceptions

Modern C++ emphasizes exceptions, not error codes, as the best way to report and handle error conditions. For more information, see Modern C++ best practices for exceptions and error handling.

std::atomic

Use the C++ Standard Library std::atomic struct and related types for inter-thread communication mechanisms.

std::variant (C++17)

Unions are commonly used in C-style programming to conserve memory by enabling members of different types to occupy the same memory location. However, unions aren’t type-safe and are prone to programming errors. C++17 introduces the std::variant class as a more robust and safe alternative to unions. The std::visit function can be used to access the members of a variant type in a type-safe manner.

Explaining some simple code

The below is an exam question:

For the second and the fourth lines above, name what type of statement that line is. Will they call the same member function of class string? [5 marks]

Therefore they both are calling 2 different member functions.

Is the above an acceptable answer? Is there anything I can add of do I have the wrong idea?

2 Answers 2

Trending sort

Trending sort is based off of the default sorting method — by highest score — but it boosts votes that have happened recently, helping to surface more up-to-date answers.

It falls back to sorting by highest score if no posts are trending.

Switch to Trending sort

About your answer regarding Line #4

You cannot be certain that it actually makes use of the copy constructor, and it absolutely shouldn’t.

Why create a temporary object inside std::string::operator= when you could copy the data from s1 into s3 directly?

What you wrote about operator= is correct, but leave out what you wrote about the copy-constructor there. There is no initialization of a new object, therefor no constructor should be called.

You should also leave out the statement regarding making copies of all the member variables, that doesn’t have to be true.

And when it comes to objects such as std::string there are pointers as members that aren’t copied, but the memory where they point are being copied into a new memory space (to be used by the destination object).

Post OP edit of his/hers post..

OP just changed his post deleting what I made a remark on in the first part of this post.

.Line 4 is also using the copy constructor to copy over all the member variables from s1 into s2

No. Line 4 is invoking copy-assignment operator, not the copy-constructor.

Note that you can disable operator= for your class if you think the copy-assignment of objects of your class doesn’t make sense. To disable this, all you need to do is, declare the operator= in the private section of your class, and then don’t provide any definition for it. Something like this:

Likewise, you can disable both : copy-constructor and copy-assignment. For example, the standard library has disabled copy-semantics for all stream classes.

In C++11, you can disable copy-semantic explicitly as:

Prgramming a pong game in ANSI C

In this tutorial I will teach you about some basics of the C programming language. We will code a simple pong game that you can play with a buddy. There are not a lot of pure C tutorials and games out there. It is an older language and is mostly used for systems and library programming. That shouldn’t stop you though. The standard hasn’t stopped evolving through the years along with the C++ programming standard.

Before continuing

To completely understand the contents of this article you should know:

Project structure

We need to start from somewher and this would be the project structure. I use CMake but if you’re familiar with other build tools and environments feel free to use them instead and just follow skip to the code part.

To structure the project it would be best to separate the source files in their own folder (clean root folder means easier orientation).

The root CMakeLists.txt file will contain the basic setup and dependencies management. The one contained in Pong will contain the list of source files and the project executable. This kind of structure allows for defining several executables or libraries like unit testing or other dependencies.

The root cmake file will contain the following code:

The cmake file in the pong directory will contain the following code initially:

We also need to define some code for our main.h and main.c files so that we can successfully compile the program. I will start with a simple main function that we will later extend until the game is complete.

When creating functions later I will intentionally skip on some details like defining function signatures in the header. There are more than a million ways to write code for a pong game. What I want to do is challenge my readers. For you to find a way to compile your own solution using my guidelines instead of giving my ready-made solution. If you want to take a look at the final implementation you can always find the source code for the pong game in the ansi-c branch of my pong repository.

The program should now compile and run without any output.

Note: If you need help with compiling using CMake you can get a quick reminder in this article about working with cmake.

Creating the window

Next step in our programming adventure is to create and render the window. For this we need to modify our main file structure. Usually in games you would have a main “game loop” which runs until the application is terminated. This loop would update some values and render on the screen. If we take this in consideration we should probably separate the code into small size chunks by creating some functions.

To initialize the window we use the Raylib funciton “InitWindow” by passing it the size and title that we want. It is also a good idea to set a target FPS for our game – its up to you how fast you want the game to update. Drawing is done by the video card (GPU) but we prepare the draw calls in the processor (CPU). We need to say when the frame drawing begins and when it ends by using the funcitons BeginDrawing and EndDrawing. We can also add a background color to our game and this should be the first thing we call every frame by using the ClearBackground function.

After successful compilation of this code we should be greeted with a window that we can move around. It will have a black background as in the draw method we use BLACK to clear the window. You’re free to choose your own windows sizes and colors this is just what I go for.

Drawing the board and score

The next step will be to draw something on the screen. Raylib makes it really easy to draw to the screen. If you want to see what is available in this library you can visit the raylib cheatsheet. Now lets add a middle line and some score. In the C language primitive data (numbers, characters, etc.) can be combined into chunks called structs. One such struct is Vector2 defined by raylib and represents two numbers for coordinates – x and y. We would need the Vector2 to define the start and end position of the line:

This should add a nice separator line starting 5 pixels from the middle top of the window and ending just 5 pixels before the bottom middle part.

Next is the score. I like to put the score in the middle. If you would like it somewhere else you can always modify the calculations. It is easy to put text on the right of the separating line as it grows to the right. This is not the same with the left. When the score grows on the left we need to push it to the left. For this we would need to measure the rendered text. First we will use the function TextFormat to make our numbers to strings. Then we will use the MeasureText function that will say how long our text will end up using the default font provided in Raylib (we pass the text and the pixel size). Then we draw the text on the screen.

When drawing with raylib consider that the coordinates (0, 0) are on the top-left part of the screen. They are measured in pixels and X grows positively to the right while Y grows positively downwards. Also element positions are the on the top left so when we specify the coordinates for the text we do so by telling where the first character on the left is located.

These small calculations to the positioning will make all the difference on how the end game will look! Now you know how to draw some basic elements like text and lines on the window. For the ball and pads we will use one more methods shown later – DrawRectangle – that accepts position, size and color.

Programming the pads

When I program things I like to separate them into descriptable chunks. Because of this we define our pads with a control scheme, position, size, speed and score. The control scheme would also define an up button and a down button. This is done so that the two pads are controllable by different buttons on the keyboard.

I will also define two functions that will take the pads for update and draw. Functions will accept a pointer to the struct so that the data is the same as the calling function and not copied. We will check input inside the update function to see if the player pressed a button last frame. Then we need to see how much the player should move. Speed is a function of time meaning it defines how much in space we would move for a certain amount of time – in our case a second. GetFrameTime would return the time in seconds as a float – meaning if half a second has passed we would get 0.5 as a value. We multiply that with the speed and we move the pad with that many pixels.

Adding the ball

We need to do something similar to the ball but isntead from input it will move on its own every frame. It is useful to add a function to detect if the ball touches one of the pads. The ball can have a constant velocity.

And the implementation is quite simple – move ball by velocity every frame and draw a rectangle on its position. The detection function would check if the ball position is inside the rectangle of the pad. This is simpler than collision detection between two rectangles but it is all we need. Always be careful to not overcomplicate your games with more code than you need.

Mixing it all together

In the previous two sections we defined some data types and update functions for them but we have not yet mixed them into our game loop. Our game loop needs to also hold on to these values so that it can pass them around the update functions so we could also create a simple struct called GameData to hold the values:

This should be enough to initialize our for both players. I give you some direct reference values but you can vary them until you like how the game plays out. We also need to add code for updating the pads and ball and drawing them on the screen:

There is only one last part missing before the game is completed for playing. This is the rules of the game. If the ball exits the screen on left or right it should bring a point to one of the players. The ball should also reset ot the center. If the ball hits a pad its velocity should get reflected on X. Also if it hits the screen on top or bottom it should be reflected on Y.

Conclusion

I hope you learned something valuable in this quick tutorial. I intentionally don’t cover every part of the code here. That way you can solve some of the problems on your own. This will be the most valuable lesson I can teach you. You can always refer to the source code. If you need more game ideas check my article about a few of those for beginners.

Comments:

Hi, thanks for this nice tutorial. I am a beginner and trying to catch up but announced as ANSI C the pong game does not work out as expected. the example code on github is clearly cpp, not ye goode olde C code. I setup the whole thing in C on codeblocks IDE with raylib properly setup and linked to the shared libs. The whole thing compiles after several tiny changes (most including the header files again or defining variables), but leaves me with an eventually blank window. 🙂 in the beginning, I wanted to learn how to handle concurrent events by event handlers and event loops but when I realised this all is managed by the raylib it was to late for me to return. I was already too deep in the rabbit hole. Now I would like to finish this little game at least before turning to something else. Probably, I am missing something essentially completely (also from the tutorial. Do you mind having a look? link to github

Hi, Jens, In my github sxample there is a branch with the ansi C version of the game. I will write you additionaly when I take a look at your code.

I’m relearning C++ and I found myself often writing pieces of code like this:

5 Answers 5

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You can use a for loop. We can declare Line in the variable declaration part and use the condition and increment parts to read and place the line. That gives you

more or less, putting everything in the condition?

You can do this

It works because && is short-circuited and because the comma-operator evaluates the first operand, discards the result and returns the result of the second operand.

So it is possible, but why would you want to do that? Making code as dense as possible is rarely good for readability (actually your original code is more readable and uses less characters).

Well, at the expense of some obfuscation,

But as a rule of thumb, work with the language, not against it. My answer is doing the latter. The way you present the code in your question is adequate.

At the risk of «but that is exactly OP’s code!», I would personally favor this version if this is the entire body of a scope (e.g. function that parses the text):

Alternatively, if part of a larger scope, I would probably group all four lines together and add empty lines before and after for visual coherence (and maybe add a short comment before it):

I am aware that this introduces no clever tricks, but this is the most compact and readable form of the given code, at least to me.

If you wanted compactness above all else, you could choose garbage variables, omit all unnecessary whitespace and even alias the types beforehand (since we are «often writing» this kind of code this is a one-off) to, say, V t;S l;while(getline(cin,l))t.push_back(l); but nobody wants to read that.

So clearly there is more than compactness at play. As for me, I’m looking to keep noise to a minimum while retaining intuitive readability, and I would suggest this is an agreeable goal.

I would never use the «throw everything into the loop condition» suggestions because that very much breaks how I expect code to be structured: The main purpose of your loop goes into the loop body. You may disagree/have different expectations, but in my eyes everything else is just an attempt to show off your minifying skills, it does not produce good code.

This would be an ideal loop to me: The condition only checks for termination and the loop body is only the operation we want to repeat.

Even better would be a standard algorithm, but I unaware of any that would help here (ranges or boost might provide, I don’t know).

On a more abstract level, if OP frequently writes this exact code, it should obviously be a separate function. But even if not, the «lots of other code» example would benefit from that abstraction too.

Simple C code snippets

I have a great difficulty in understanding the printed values of these 2 source codes.

Prints out: » 0, garbage value, same garbage value +1, same garbage value +2 «.

Shouldn’t any uninitialized object in the main function (or any other functon ) be assigned a random (garbage) value?

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The value of uninitialized automatic variables is indeterminate and so if you don’t talk about a specific compiler on a specific machine with a specific set of flags then it is really unpredictable. Even if you talk about a very specific platform and settings you still may not get reproducible results.

On modern systems automatic variables will often be allocated on the stack and you may get the same memory location and therefore you would then see three consecutive values. But you should not rely on this behavior and using uninitialized variables is undefined behavior and the results are unpredictable.

The C99 draft standard tell us in section 6.7.8 Initialization paragraph 10 that:

If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate.

and tell us in the definitions of indeterminate value :

either an unspecified value or a trap representation

What is undefined behavior? In the strictest sense it is behavior the C standard does not impose requirements on, it is construct of the standard. It is defined in the draft standard in section 3.4.3 :

behavior, upon use of a nonportable or erroneous program construct or of erroneous data, for which this International Standard imposes no requirements

and has the following note:

Possible undefined behavior ranges from ignoring the situation completely with unpredictable results, to behaving during translation or program execution in a documented manner characteristic of the environment (with or without the issuance of a diagnostic message), to terminating a translation or execution (with the issuance of a diagnostic message).

at the end of the day it is a trade off between designing an efficient language and a safe one, which is paraphrased from What Every C Programmer Should Know About Undefined Behavior #1/3.

Here are more links to better understanding undefined behavior:

Table of Contents

Concepts are a revolutionary approach for writing templates! They allow you to put constraints on template parameters that improve the readability of code, speed up compilation time, and give better error messages.

Read on and learn how to use them in your code!

What is a concept?
In short, a concept is a set of constraints on template parameters evaluated at compile time. You can use them for class templates and function templates to control function overloads and partial specialization.
Here’s an example of a simple concept:
The above code defines the integral concept. As you can see, it looks similar to other template<> constructs.
We can also define another one using a requires expression:
This one looks a bit more serious! But after some time, it seems “readable”:
Those two examples should give you a taste; let’s try to use them in some real code.

How to use concepts
In one of the most common case, for a small function template, you’ll see the following syntax:
You can also use requires clause as the last part of a function declaration:
The key part is the requires clause. It allows us to specify various requirements on the input template parameters.
Let’s look at a simple function template that computes an average of an input container.
With the above source code, I used two concepts available in the standard library ( std::integral and std::floating_point ) and combined them together.

One advantage: better compiler errors
If you play with the previous example and write:
It’s pretty nice!
Usually, with templates, before the concepts feature, you could get some long cryptic messages about some failed operation that is not possible on a given type in some deep level of the call stack.

Predefined Concepts
Here’s the list of predefined concepts that we get in C++20 with header:
Core language concepts Notes
same_as
derived_from
convertible_to
common_reference_with
common_with
integral
signed_integral
unsigned_integral
floating_point
assignable_from
swappable / swappable_with
destructible
constructible_from
default_initializable
move_constructible
copy_constructible
Comparison concepts Notes
boolean-testable a type can be used in boolean test cases
equality_comparable / equality_comparable_with
totally_ordered / totally_ordered_with Defined in
three_way_comparable / three_way_comparable_with
Object concepts Notes
movable
copyable
semiregular a type can be copied, moved, swapped, and default constructed
regular a type is both semiregular and equality_comparable
Callable concepts Notes
invocable / regular_invocable
predicate
relation specifies a binary relation
equivalence_relation
strict_weak_order
And here’s my separate blog post on the Callable concepts:

Core language concepts	Notes
same_as
derived_from
convertible_to
common_reference_with
common_with
integral
signed_integral
unsigned_integral
floating_point
assignable_from
swappable / swappable_with
destructible
constructible_from
default_initializable
move_constructible
copy_constructible

Comparison concepts	Notes
boolean-testable	a type can be used in boolean test cases
equality_comparable / equality_comparable_with
totally_ordered / totally_ordered_with	Defined in
three_way_comparable / three_way_comparable_with

Object concepts	Notes
movable
copyable
semiregular	a type can be copied, moved, swapped, and default constructed
regular	a type is both semiregular and equality_comparable

Callable concepts	Notes
invocable / regular_invocable
predicate
relation	specifies a binary relation
equivalence_relation
strict_weak_order

Code Simplification
As you could see, the syntax for concepts and constraints is relatively easy, but still, in C++20, we got much more!
There are various shortcuts and terse syntax that allow us to make template code super simple.
We have several things:
We can “compress” it into:
And it expands into:
It looks similar to what we get with C++14 and generic lambdas (Lambda Week: Going Generic).
Additionally, we can also use constrained auto :
What’s more, rather than specifying template requires. you can write:

The requires expression
One of the most powerful items with concepts is the requires keyword. It has two forms:
The last one is very flexible and allows to specify quite advanced constraints. In the introduction you’ve seen one case with a detection of buildHtml() member function. Here’s another example:
The above concept restricts an “interface” for basic clocks. We require that it has the three member functions, but we don’t specify what type do they return.
From one perspective, we can say that the requires expression takes a type and tries to instantiate the specified requirements. If it fails, then a given class doesn’t comply with this concept. It’s like SFINAE but in a friendly and easy-to-express syntax.
I just showed some basic examples to give you a taste, but look at this article from A. Krzemienski: Requires-expression | Andrzej’s C++ blog which expends this topic in more depth.

The updated Detection Idiom
Thanks to Concepts we can now easily detect a function, a member function or even a particular overload. This is much simpler that with complicated SFINAE techniques that we had before.

Compiler Support

Summary
It’s just a tip of an iceberg!
Additionally, the Standard Library is equipped with a set of predefined concepts (mainly obtained from existing type traits), making it easier to start.
What’s more, C++20 offers even more language features to make the syntax even more compact. It’s mostly due to constrained auto. In some cases, you won’t even need to write template <> at the front of your function template!
What I like about this feature is that you can introduce it slowly in your code. You can add concepts here and there, experiment, see how it works. And then gradually use more advanced constructs and apply in other places.

Back to you

Have you tried concepts? What are your first thoughts on that feature?

What are the most important use cases for you?

Share your comments below the article.

References
I’ve prepared a valuable bonus if you’re interested in Modern C++!
Learn all major features of recent C++ Standards!
Check it out here:

Structure of a program

The best way to learn a programming language is by writing programs. Typically, the first program beginners write is a program called «Hello World», which simply prints «Hello World» to your computer screen. Although it is very simple, it contains all the fundamental components C++ programs have:

The left panel above shows the C++ code for this program. The right panel shows the result when the program is executed by a computer. The grey numbers to the left of the panels are line numbers to make discussing programs and researching errors easier. They are not part of the program.

Let’s examine this program line by line:

The function named main is a special function in all C++ programs; it is the function called when the program is run. The execution of all C++ programs begins with the main function, regardless of where the function is actually located within the code.
Lines 5 and 7: < and >The open brace ( < ) at line 5 indicates the beginning of main 's function definition, and the closing brace ( >) at line 7, indicates its end. Everything between these braces is the function’s body that defines what happens when main is called. All functions use braces to indicate the beginning and end of their definitions.

Line 6: std::cout This line is a C++ statement. A statement is an expression that can actually produce some effect. It is the meat of a program, specifying its actual behavior. Statements are executed in the same order that they appear within a function’s body.

Notice that the statement ends with a semicolon ( ; ). This character marks the end of the statement, just as the period ends a sentence in English. All C++ statements must end with a semicolon character. One of the most common syntax errors in C++ is forgetting to end a statement with a semicolon.

You may have noticed that not all the lines of this program perform actions when the code is executed. There is a line containing a comment (beginning with // ). There is a line with a directive for the preprocessor (beginning with # ). There is a line that defines a function (in this case, the main function). And, finally, a line with a statements ending with a semicolon (the insertion into cout ), which was within the block delimited by the braces ( < >) of the main function.

The program has been structured in different lines and properly indented, in order to make it easier to understand for the humans reading it. But C++ does not have strict rules on indentation or on how to split instructions in different lines. For example, instead of

We could have written:

all in a single line, and this would have had exactly the same meaning as the preceding code.

In C++, the separation between statements is specified with an ending semicolon ( ; ), with the separation into different lines not mattering at all for this purpose. Many statements can be written in a single line, or each statement can be in its own line. The division of code in different lines serves only to make it more legible and schematic for the humans that may read it, but has no effect on the actual behavior of the program.

Now, let’s add an additional statement to our first program:

In this case, the program performed two insertions into std::cout in two different statements. Once again, the separation in different lines of code simply gives greater readability to the program, since main could have been perfectly valid defined in this way:

The source code could have also been divided into more code lines instead:

And the result would again have been exactly the same as in the previous examples.

Preprocessor directives (those that begin by # ) are out of this general rule since they are not statements. They are lines read and processed by the preprocessor before proper compilation begins. Preprocessor directives must be specified in their own line and, because they are not statements, do not have to end with a semicolon ( ; ).

Comments

As noted above, comments do not affect the operation of the program; however, they provide an important tool to document directly within the source code what the program does and how it operates.

C++ supports two ways of commenting code:

The first of them, known as line comment, discards everything from where the pair of slash signs ( // ) are found up to the end of that same line. The second one, known as block comment, discards everything between the /* characters and the first appearance of the */ characters, with the possibility of including multiple lines.

Let’s add comments to our second program:

Using namespace std

In order to refer to the elements in the std namespace a program shall either qualify each and every use of elements of the library (as we have done by prefixing cout with std:: ), or introduce visibility of its components. The most typical way to introduce visibility of these components is by means of using declarations:

The above declaration allows all elements in the std namespace to be accessed in an unqualified manner (without the std:: prefix).

With this in mind, the last example can be rewritten to make unqualified uses of cout as:

Both ways of accessing the elements of the std namespace (explicit qualification and using declarations) are valid in C++ and produce the exact same behavior. For simplicity, and to improve readability, the examples in these tutorials will more often use this latter approach with using declarations, although note that explicit qualification is the only way to guarantee that name collisions never happen.

Prerequisites

Create the app

Start Visual Studio Code.

Select File > Open Folder (File > Open. on macOS) from the main menu.

In the Open Folder dialog, create a HelloWorld folder and select it. Then click Select Folder (Open on macOS).

In the Do you trust the authors of the files in this folder? dialog, select Yes, I trust the authors.

Open the Terminal in Visual Studio Code by selecting View > Terminal from the main menu.

The Terminal opens with the command prompt in the HelloWorld folder.

In the Terminal, enter the following command:

The project template creates a simple application that displays «Hello World» in the console window by calling the Console.WriteLine(String) method in Program.cs.

Replace the contents of Program.cs with the following code:

The first time you edit a .cs file, Visual Studio Code prompts you to add the missing assets to build and debug your app. Select Yes, and Visual Studio Code creates a .vscode folder with launch.json and tasks.json files.

If you don’t get the prompt, or if you accidentally dismiss it without selecting Yes, do the following steps to create launch.json and tasks.json:

In the latest version of C#, a new feature named top-level statements lets you omit the Program class and the Main method. Most existing C# programs don’t use top-level statements, so this tutorial doesn’t use this new feature. But it’s available in C# 10, and whether you use it in your programs is a matter of style preference.

Run the app

Run the following command in the Terminal:

The program displays «Hello World!» and ends.

Enhance the app

Enhance the application to prompt the user for their name and display it along with the date and time.

NewLine is a platform-independent and language-independent way to represent a line break. Alternatives are \n in C# and vbCrLf in Visual Basic.

Save your changes.

In Visual Studio Code, you have to explicitly save changes. Unlike Visual Studio, file changes are not automatically saved when you build and run an app.

Run the program again:

Respond to the prompt by entering a name and pressing the Enter key.

Press any key to exit the program.

Additional resources

Next steps

Prerequisites

Create the app

Start Visual Studio Code.

Select File > Open Folder (File > Open. on macOS) from the main menu.

In the Open Folder dialog, create a HelloWorld folder and click Select Folder (Open on macOS).

Open the Terminal in Visual Studio Code by selecting View > Terminal from the main menu.

The Terminal opens with the command prompt in the HelloWorld folder.

In the Terminal, enter the following command:

The template creates a simple «Hello World» application. It calls the Console.WriteLine(String) method to display » Hello World! » in the console window.

Main is the application entry point, the method that’s called automatically by the runtime when it launches the application. Any command-line arguments supplied when the application is launched are available in the args array.

Run the app

Run the following command in the Terminal:

The program displays «Hello World!» and ends.

Enhance the app

Enhance the application to prompt the user for their name and display it along with the date and time.

Open Program.cs by clicking on it.

The first time you open a C# file in Visual Studio Code, OmniSharp loads in the editor.

Select Yes when Visual Studio Code prompts you to add the missing assets to build and debug your app.

NewLine is a platform-independent and language-independent way to represent a line break. Alternatives are \n in C# and vbCrLf in Visual Basic.

Save your changes.

In Visual Studio Code, you have to explicitly save changes. Unlike Visual Studio, file changes are not automatically saved when you build and run an app.

Run the program again:

Respond to the prompt by entering a name and pressing the Enter key.

Press any key to exit the program.

Additional resources

Next steps

Simple C++ code to generate Armstrong numbers [closed]

The following is my simple attempt at generating Armstrong numbers. But it only outputs «1». What might be wrong?

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You need to always set sum = 0 inside the for-i-loop.

Armstrong numbers: n-digit numbers equal to sum of n-th powers of their digits.

‘r*r*r’ isn’t n’th power of the number.

The first thing is that you’re assuming that n (as in the nth power) is always three (in your r*r*r ). That’s only true if your initial value has three digits (as with the 153 example).

You need to count the digits in your initial number to calculate n, and then replace your r*r*r with raising r to the nth power.

This doesn’t explain why 153 isn’t found, though. The reason for that is because you aren’t reseting sum to zero unless you find a match. You need to reset it to zero whether you found a match or not.

you can calculate n using log:

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SimpleCode: редактор кода с подсветкой синтаксиса для Simple UI

Для всех, кто пользуется разработкой Дмитрия Воронцова Simple UI, предлагается расширение для подсветки синтаксиса языка 1С.

Код редактора взят из многочисленных публикаций на Инфостарте.

При открытии формы Экрана Simple UI, тексты модулей автоматически подгружаются в поля типа HTML. Для совместимости оставлено текстовое поле, из которого удобно копировать тексты модулей (на некоторых платформах или при использовании ВЭБ клиентов копирование текстов из HTML полей затруднено). Если при открытии форма экрана тексты не «подтянулись», существует кнопка «Перечитать», повторяющая это действие.

Тестировалось в следующих условиях:

ОС Windows 10 x64, релизы платформы 8.3.16.1148, 8.3.17.1386.

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Оказалось, что стандартная консоль от 1С не умеет работать с параметрами типа ВнешниеИсточникиДанных. Добавил возможность заполнения параметров данного типа и заодно улучшил работу с параметрами-списками значений

23.08.2021 1998 6 wenzor 0

Печать WORD из тонкого клиента с доступом по вэб адресу (управляемые формы)

Вариант печати файлов WORD из 1С из-под тонкого клиента, подключенного по вэб адресу. В файле показан вариант печати динамических таблиц, то есть таблиц с изменяемым количеством строк. Обработка печати довольно простая. Опробована на Управление торговлей, редакция 11 (11.4.13.155), версия платформы 1С:Предприятие 8.3 (8.3.18.1334)

10.06.2021 3372 5 user810754 1

Удаление и/или копирование сохраненных в 1С настроек (например настроек печати табличных форм) Промо

Иногда нужно удалить сохраненную в 1С «покореженную» настройку или скопировать «удачную» другому пользователю.

01.09.2012 71986 1401 AnryMc 46

Подсистема обработки событий в 1С

Универсальное расширение для регистрации событий о действиях пользователей в системе 1С и рассылки уведомлений об этих событиях.

07.06.2021 6734 42 elcoan 5

Подсистема «Показатели объектов»

06.03.2021 10781 6 pila86 16

Подсистема универсальных предопределенных значений

Готовая подсистема универсальных предопределенных значений упрощает определение объектов в базе данных для разработчиков. При внедренном справочнике «Универсальные предопределенные значения» разработчику достаточно добавить элемент справочника и задать значение объекта конфигурации, чтобы потом использовать наименование элемента при получении значения в определенных строках кода.

01.03.2021 2287 2 Denis211990 12

Программа Faster 9.4 позволяет ускорить процесс работы программиста (работает в любом текстовом редакторе). Подсказка при вводе текста на основе ранее введенного текста и настроенных шаблонов. Программа Faster позволяет делится кодом с другими программистами в два клика или передать ссылку через QR Код. Исправление введенных фраз двойным Shift (с помощью speller.yandex). Переводчик текста. Переворачивает текст случайно набранный на другой раскладке. Полезная утилита для тех, кто печатает много однотипного текста, кодирует в среде Windows на разных языках программирования. Через некоторое время работы с программой у вас соберется своя база часто используемых словосочетаний и кусков кода. Настройка любых шорткатов под себя с помощью скриптов. Никаких установок и лицензий, все бесплатно.

24.05.2012 89794 972 moolex 157

«Все функции» только для объектов расширений

Показывает только объекты ваших расширений. Быстрый доступ к вашим объектам, не нужно постоянно нажимать «Функции для технического специалиста» («Все функции»)

28.02.2021 4046 6 t278 1

FormCodeGenerator Программная доработка форм. Часть 2 (Режим работы «Режим сравнения форм») на примере ERP 2.5

Данная публикация является продолжением описания функционирования обработки «FormCodeGenerator » в режиме сравнения форм и генерирования кода на основании сравнения. Подходит для перевода уже доработанных форм с интерактивной доработки на программную. Данный режим работы обработки снизит издержки при дальнейших обновлениях конфигураций.

21.12.2020 14611 27 huxuxuya 11

Примеры синтеза речи и воспроизведения WAV файлов с помощью библиотеки Microsoft Speech Application Programming Interface (Speech API, SAPI)

Примеры синтеза речи и воспроизведения WAV файлов с помощью библиотеки программ для Windows, позволяющей распознавать и(или) синтезировать голос. Может использоваться как учебный пример.

20.11.2020 3183 2 Hitcher 1

Консоль запросов с графом (Анализатор сложных запросов) Промо

Консоль запросов для анализа запросов с большим количеством временных таблиц и вложенных запросов. Отображает структуру взаимосвязей временных таблиц в виде графа. Позволяет быстро передвигаться по тексту запроса и получать результат выполнения подзапросов. Единственная консоль запросов, которая позволяет выводить результат выполнения вложенных запросов и любой части объединения запроса. Удобное получение данных запроса из отладчика включая временные таблицы. Текст запроса в структурированном виде (можно свернуть, развернуть текст подзапроса). И еще много другого, чего вы не найдете в других консолях запросов. Поддержка УФ и ОФ. Версия 0.9.1 от 18.10.2019 (поддержка WebKit).

03.05.2017 111248 525 manuel 294

Внешний регламент для 1С

Внешний регламент сделан для тех, кто ценит свое время и время заказчика. После одноразового встраивания в конфигурацию, внешний регламент на лету позволяет добавлять, изменять внешние модули, которые могут выполнятся как регламентные задачи с указанным интервалом или запускаться в ручном режиме для отладки. Все модули (внешние обработки) находятся и выполняются на стороне сервера, что позволяет исключить подмену алгоритмов со стороны клиента.

05.03.2020 12530 10 moolex 12

CF & SQL : конструктор прямых запросов к БД 1С

Программа для чтения и анализа внутренней структуры данных 1С V8.х, Содержит конструктор прямых SQL запросов, позволяет обрабатывать и редактировать тексты SQL-запросов, выполнять прямые запросы к базе данных 1С и обрабатывать полученные результаты.

02.10.2019 38059 358 dmitrydemenew 66

Markdown-editor в 1С (с сохранением в HTML)

В этой обработке вы пишете свой текст, используя синтаксис Markdown, а на выходе получаете чистый HTML-код, избавленный от JS-библиотеки, которая его сформировала. Совместим с Webkit и IE.

04.07.2019 16349 29 riposte 6

Установка баз данных из Проводника Промо

28.10.2013 42292 106 Evil Beaver 30

Запуск 1С под любым пользователем (без необходимости указания пароля)

Предназначается для запуска сеанса другого пользователя из своего сеанса 1С (если пароль вам неизвестен).

02.07.2019 34936 394 sapervodichka 0

Модель объекта

Подсистема позволяет описать модель данных объекта, где описана зависимость между реквизитами, и затем использовать эту модель в разных сценариях работы с объектом. Версия платформы: 8.3.6 и выше. С небольшими доработками будет работать на 8.2.

30.06.2019 20231 1 vadim1980 5

Блин, мы забыли включить регламентные задания…

Привет, Инфостарт! Сегодня расскажу, как я решил проблему с выключенными регламентными заданиями в рабочих базах. Желая исключить человеческий фактор и минимизировать количество ошибок, я написал небольшую конфигурацию. В конфигурации два регламентных задания. Первое периодически подключается к кластеру и сохраняет текущие параметры: имя, Сервер БД, базу СУДБ, блокировки входа и регламентных заданий и т.д. Второе задание периодически проверяет эти параметры на ошибки.

08.04.2019 29870 22 slozhenikin_com 37

Simple WMS Client – это визуальный конструктор мобильного клиента для терминала сбора данных(ТСД) или обычного телефона на Android. Приложение работает в онлайн режиме через интернет или WI-FI, постоянно общаясь с базой посредством http-запросов (вариант для 1С-клиента общается с 1С напрямую как обычный клиент). Можно создавать любые конфигурации мобильного клиента с помощью конструктора и обработчиков на языке 1С (НЕ мобильная платформа). Вся логика приложения и интеграции содержится в обработчиках на стороне 1С. Это очень простой способ создать и развернуть клиентскую часть для WMS системы или для любой другой конфигурации 1С (УТ, УПП, ERP, самописной) с минимумом программирования. Например, можно добавить в учетную систему адресное хранение, учет оборудования и любые другие задачи. Приложение умеет работать не только со штрих-кодами, но и с распознаванием голоса от Google. Это бесплатная и открытая система, не требующая обучения, с возможностью быстро получить результат.

09.01.2019 69643 278 informa1555 239

Легкое и гибкое управление списком доступных баз 1С у пользователей

Когда в локальной сети много пользователей, а еще большое количество различных баз и при этом каждому нужны свои, то администрирование этого зоопарка превращается в АД! Этот комплекс позволяет централизованно управлять списком доступных баз в разрезе пользователей. За пару кликов можно добавить или убрать базу у всех пользователей.

05.12.2018 25810 27 RomikR 11

Очистка кэша 1С 8 (8.0, 8.1, 8.2, 8.3). Грамотная чистка кэша 1С с сохранением настроек.

04.11.2018 60723 592 Eugen-S 36

Управляемая консоль запросов, отчетов 3.8.9 (расширение, внешняя обработка)

Работа с запросом и СКД, Полная поддержка пакетных запросов, временных таблиц, Сравнение результатов, текстов, Разбор структуры запроса в виде дерева, Анализ плана запроса, Групповая обработка

14.08.2018 141679 3285 Evg-Lylyk 794

Позиционирование в помещении с помощью нейросети по сигналу Wi-Fi. Интерактивная карта склада в 1С с показом позиции

09.08.2018 41621 35 informa1555 30

How to compile your C++ code in Visual Studio Code

PS: This was published on my Blog here.

C++ is a statically-typed, free-form, (usually) compiled, multi-paradigm, intermediate-level general-purpose middle-level programming language.

In simple terms, C++ is a sophisticated, efficient, general-purpose programming language based on C.

It was developed by Bjarne Stroustrup in 1979.

One of C++’s main features is the compiler. This is used to compile and run C++ code.

A compiler is a special program that processes statements written in a particular programming language like C++ and turns them into machine language or «code» that a computer’s processor uses. (Source)

I actually wrote this article because I had a C++ assignment which required using a compiler. As usual, everyone was using the CodeBlocks IDE and Visual Studio IDE. But I was already used to Visual Studio Code for all my programming stuff.

I then set out to find a way of compiling C++ directly inside my own VsCode Editor, hence this article :).

In this article, I’ll show you how to set up your compiler in VsCode and give you some links to some of the best C++ resources.

Prerequisites

Disclaimer!

I will be using a Windows OS throughout this article, but I’ll provide links to resources that will help those using other operating systems.

Now let’s get started!

Download and install a C++ compiler

MinGW, a contraction of «Minimalist GNU for Windows», is a minimalist development environment for native Microsoft Windows applications. (Source)

Edit your PATH environment variable to include the directory where the C++ compiler is located

Install Code Runner extension in VS Code

Now we have our compiler set up, let’s install Code Runner

Code Runner allows you to Run code snippet or code file for multiple languages:

Save this file as test.cpp

Run your code using Code Runner

The code will run and the output will be shown in the Output Window. Open the output window with `Ctrl+ shortcut.

To stop the running code

Hurray, you just successfully set up your C++ environment in VsCode!

Conclusion

Here’s a quick hint: By default, VsCode’s output terminal is read-only. If you’re running code that requires user input like:

Hurray, you’re done and ready to roll :).

C++ resources

Here are some C++ resources you can use to get started with learning C++

Module 1. Your First Windows Program

In this module, we will write a minimal Windows desktop program. All it does is create and show a blank window. This first program contains about 50 lines of code, not counting blank lines and comments. It will be our starting point; later we’ll add graphics, text, user input, and other features.

If you are looking for more details on how to create a traditional Windows desktop application in Visual Studio, check out Walkthrough: Create a traditional Windows Desktop application (C++).

Here is the complete code for the program:

You can download the complete Visual Studio project from Windows Hello World Sample.

It may be useful to give a brief outline of what this code does. Later topics will examine the code in detail.

Notice that the program does not explicitly call the WindowProc function, even though we said this is where most of the application logic is defined. Windows communicates with your program by passing it a series of messages. The code inside the while loop drives this process. Each time the program calls the DispatchMessage function, it indirectly causes Windows to invoke the WindowProc function, once for each message.

Simple console text editor

I have been following along Gary Bernhardt’s excellent video series on «Building a Text Editor From Scratch». It’s in Ruby but I wanted to do it in C# just to see how much it differs.

Implementation wise it’s faithful to what he does. I do have questions whether the code is up to mark in terms of new C# conventions, haven’t violated any biggies or gone overboard with LINQ.

The method SplitLine was a head scratcher (really showcased the terseness of Ruby) where his line splitting and new carriage code looks like and I couldn’t come up with anything like it in C#.

1 Answer 1

There are a couple of simple errors:

1) In Buffer.SplitLine(. ) you replace the next line with the second part of the split instead of inserting it after the first part:

instead you should do something like this:

2) In Cursor.MoveToCol(int col) you don’t use the argument col:

I suppose it to be:

In Editor.HandleInput() you should check if a character is a text char before you insert:

Other things

Consider if this input check is suitable:

In this way you’ll save the other combinations with Control + Q to other tools.

Your handling of state is nice and clean and easily maintained in that you always create a new instance when ever Buffer or Cursor changes. But it requires immutable objects. Cursor is not immutable :

Anyone (?) could change these parameters on objects placed on the history stack.

Simple Calculator with switch statement

I just start learning to code in C#. Is there any other short way to make calculator like this

1 Answer 1

Is there any other short way to make calculator

Without trying to be facetious, of course there are many different ways to try and do the same thing.

I assume this is a beginner exercise; so I’ll review it with that in mind, giving you some tips on what to tackle next as well.

The coding style

The code itself

Improvements and future challenges

Small remark

Is there any other short way

Shortness is not a measure of good code. If anything, excessively short code is often bad due to inlining several operations and generally lowering code readability.

I know that you meant «simple», i.e. you didn’t want a counterexample that is massively more complicated than your exercise.

But I just want to call your attention to the distinction between short code and simple code. These are not freely interchangeable; and more often end up being opposites of each other.

C is a general-purpose, high-level language that was originally developed by Dennis M. Ritchie to develop the UNIX operating system at Bell Labs. C was originally first implemented on the DEC PDP-11 computer in 1972.

In 1978, Brian Kernighan and Dennis Ritchie produced the first publicly available description of C, now known as the K&R standard.

The UNIX operating system, the C compiler, and essentially all UNIX application programs have been written in C. C has now become a widely used professional language for various reasons −

Facts about C

C was invented to write an operating system called UNIX.

C is a successor of B language which was introduced around the early 1970s.

The language was formalized in 1988 by the American National Standard Institute (ANSI).

The UNIX OS was totally written in C.

Today C is the most widely used and popular System Programming Language.

Most of the state-of-the-art software have been implemented using C.

Today’s most popular Linux OS and RDBMS MySQL have been written in C.

Why use C?

C was initially used for system development work, particularly the programs that make-up the operating system. C was adopted as a system development language because it produces code that runs nearly as fast as the code written in assembly language. Some examples of the use of C might be −

C Programs

A C program can vary from 3 lines to millions of lines and it should be written into one or more text files with extension «.c»; for example, hello.c. You can use «vi», «vim» or any other text editor to write your C program into a file.

This tutorial assumes that you know how to edit a text file and how to write source code inside a program file.

Local Environment Setup

If you want to set up your environment for C programming language, you need the following two software tools available on your computer, (a) Text Editor and (b) The C Compiler.

Text Editor

This will be used to type your program. Examples of few a editors include Windows Notepad, OS Edit command, Brief, Epsilon, EMACS, and vim or vi.

The name and version of text editors can vary on different operating systems. For example, Notepad will be used on Windows, and vim or vi can be used on windows as well as on Linux or UNIX.

The files you create with your editor are called the source files and they contain the program source codes. The source files for C programs are typically named with the extension «.c«.

Before starting your programming, make sure you have one text editor in place and you have enough experience to write a computer program, save it in a file, compile it and finally execute it.

The C Compiler

The source code written in source file is the human readable source for your program. It needs to be «compiled», into machine language so that your CPU can actually execute the program as per the instructions given.

The compiler compiles the source codes into final executable programs. The most frequently used and free available compiler is the GNU C/C++ compiler, otherwise you can have compilers either from HP or Solaris if you have the respective operating systems.

The following section explains how to install GNU C/C++ compiler on various OS. We keep mentioning C/C++ together because GNU gcc compiler works for both C and C++ programming languages.

Installation on UNIX/Linux

If you are using Linux or UNIX, then check whether GCC is installed on your system by entering the following command from the command line −

If you have GNU compiler installed on your machine, then it should print a message as follows −

If GCC is not installed, then you will have to install it yourself using the detailed instructions available at https://gcc.gnu.org/install/

This tutorial has been written based on Linux and all the given examples have been compiled on the Cent OS flavor of the Linux system.

Installation on Mac OS

If you use Mac OS X, the easiest way to obtain GCC is to download the Xcode development environment from Apple’s web site and follow the simple installation instructions. Once you have Xcode setup, you will be able to use GNU compiler for C/C++.

Installation on Windows

While installing Min GW, at a minimum, you must install gcc-core, gcc-g++, binutils, and the MinGW runtime, but you may wish to install more.

Add the bin subdirectory of your MinGW installation to your PATH environment variable, so that you can specify these tools on the command line by their simple names.

After the installation is complete, you will be able to run gcc, g++, ar, ranlib, dlltool, and several other GNU tools from the Windows command line.

Before we study the basic building blocks of the C programming language, let us look at a bare minimum C program structure so that we can take it as a reference in the upcoming chapters.

Hello World Example

A C program basically consists of the following parts −

Let us look at a simple code that would print the words «Hello World» −

Let us take a look at the various parts of the above program −

The first line of the program #include is a preprocessor command, which tells a C compiler to include stdio.h file before going to actual compilation.

The next line int main() is the main function where the program execution begins.

The next line /*. */ will be ignored by the compiler and it has been put to add additional comments in the program. So such lines are called comments in the program.

The next line printf(. ) is another function available in C which causes the message «Hello, World!» to be displayed on the screen.

The next line return 0; terminates the main() function and returns the value 0.

Compile and Execute C Program

Let us see how to save the source code in a file, and how to compile and run it. Following are the simple steps −

Open a text editor and add the above-mentioned code.

Save the file as hello.c

Open a command prompt and go to the directory where you have saved the file.

Type gcc hello.c and press enter to compile your code.

If there are no errors in your code, the command prompt will take you to the next line and would generate a.out executable file.

Now, type a.out to execute your program.

You will see the output «Hello World» printed on the screen.

Make sure the gcc compiler is in your path and that you are running it in the directory containing the source file hello.c.

You have seen the basic structure of a C program, so it will be easy to understand other basic building blocks of the C programming language.

Tokens in C

A C program consists of various tokens and a token is either a keyword, an identifier, a constant, a string literal, or a symbol. For example, the following C statement consists of five tokens −

The individual tokens are −

Semicolons

In a C program, the semicolon is a statement terminator. That is, each individual statement must be ended with a semicolon. It indicates the end of one logical entity.

Given below are two different statements −

Comments

Comments are like helping text in your C program and they are ignored by the compiler. They start with /* and terminate with the characters */ as shown below −

You cannot have comments within comments and they do not occur within a string or character literals.

Identifiers

A C identifier is a name used to identify a variable, function, or any other user-defined item. An identifier starts with a letter A to Z, a to z, or an underscore ‘_’ followed by zero or more letters, underscores, and digits (0 to 9).

Keywords

The following list shows the reserved words in C. These reserved words may not be used as constants or variables or any other identifier names.

auto	else	long	switch
break	enum	register	typedef
case	extern	return	union
char	float	short	unsigned
const	for	signed	void
continue	goto	sizeof	volatile
default	if	static	while
do	int	struct	_Packed
double

Whitespace in C

A line containing only whitespace, possibly with a comment, is known as a blank line, and a C compiler totally ignores it.

Whitespace is the term used in C to describe blanks, tabs, newline characters and comments. Whitespace separates one part of a statement from another and enables the compiler to identify where one element in a statement, such as int, ends and the next element begins. Therefore, in the following statement −

there must be at least one whitespace character (usually a space) between int and age for the compiler to be able to distinguish them. On the other hand, in the following statement −

no whitespace characters are necessary between fruit and =, or between = and apples, although you are free to include some if you wish to increase readability.

Data types in c refer to an extensive system used for declaring variables or functions of different types. The type of a variable determines how much space it occupies in storage and how the bit pattern stored is interpreted.

The types in C can be classified as follows −

They are arithmetic types and are further classified into: (a) integer types and (b) floating-point types.

They are again arithmetic types and they are used to define variables that can only assign certain discrete integer values throughout the program.

The type specifier void indicates that no value is available.

They include (a) Pointer types, (b) Array types, (c) Structure types, (d) Union types and (e) Function types.

The array types and structure types are referred collectively as the aggregate types. The type of a function specifies the type of the function’s return value. We will see the basic types in the following section, where as other types will be covered in the upcoming chapters.

Integer Types

The following table provides the details of standard integer types with their storage sizes and value ranges −

To get the exact size of a type or a variable on a particular platform, you can use the sizeof operator. The expressions sizeof(type) yields the storage size of the object or type in bytes. Given below is an example to get the size of various type on a machine using different constant defined in limits.h header file −

When you compile and execute the above program, it produces the following result on Linux −

Floating-Point Types

The following table provide the details of standard floating-point types with storage sizes and value ranges and their precision −

Sr.No.	Types & Description
1

Type	Storage size	Value range	Precision
float	4 byte	1.2E-38 to 3.4E+38	6 decimal places
double	8 byte	2.3E-308 to 1.7E+308	15 decimal places
long double	10 byte	3.4E-4932 to 1.1E+4932	19 decimal places

The header file float.h defines macros that allow you to use these values and other details about the binary representation of real numbers in your programs. The following example prints the storage space taken by a float type and its range values −

When you compile and execute the above program, it produces the following result on Linux −

The void Type

The void type specifies that no value is available. It is used in three kinds of situations −

Function returns as void

There are various functions in C which do not return any value or you can say they return void. A function with no return value has the return type as void. For example, void exit (int status);

Function arguments as void

There are various functions in C which do not accept any parameter. A function with no parameter can accept a void. For example, int rand(void);

Pointers to void

A pointer of type void * represents the address of an object, but not its type. For example, a memory allocation function void *malloc( size_t size ); returns a pointer to void which can be casted to any data type.

A variable is nothing but a name given to a storage area that our programs can manipulate. Each variable in C has a specific type, which determines the size and layout of the variable’s memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

The name of a variable can be composed of letters, digits, and the underscore character. It must begin with either a letter or an underscore. Upper and lowercase letters are distinct because C is case-sensitive. Based on the basic types explained in the previous chapter, there will be the following basic variable types −

Sr.No.	Types & Description
1

Typically a single octet(one byte). It is an integer type.

The most natural size of integer for the machine.

A single-precision floating point value.

A double-precision floating point value.

Represents the absence of type.

C programming language also allows to define various other types of variables, which we will cover in subsequent chapters like Enumeration, Pointer, Array, Structure, Union, etc. For this chapter, let us study only basic variable types.

Variable Definition in C

A variable definition tells the compiler where and how much storage to create for the variable. A variable definition specifies a data type and contains a list of one or more variables of that type as follows −

Here, type must be a valid C data type including char, w_char, int, float, double, bool, or any user-defined object; and variable_list may consist of one or more identifier names separated by commas. Some valid declarations are shown here −

The line int i, j, k; declares and defines the variables i, j, and k; which instruct the compiler to create variables named i, j and k of type int.

Variables can be initialized (assigned an initial value) in their declaration. The initializer consists of an equal sign followed by a constant expression as follows −

Some examples are −

For definition without an initializer: variables with static storage duration are implicitly initialized with NULL (all bytes have the value 0); the initial value of all other variables are undefined.

Variable Declaration in C

A variable declaration provides assurance to the compiler that there exists a variable with the given type and name so that the compiler can proceed for further compilation without requiring the complete detail about the variable. A variable definition has its meaning at the time of compilation only, the compiler needs actual variable definition at the time of linking the program.

A variable declaration is useful when you are using multiple files and you define your variable in one of the files which will be available at the time of linking of the program. You will use the keyword extern to declare a variable at any place. Though you can declare a variable multiple times in your C program, it can be defined only once in a file, a function, or a block of code.

Example

Try the following example, where variables have been declared at the top, but they have been defined and initialized inside the main function −

When the above code is compiled and executed, it produces the following result −

The same concept applies on function declaration where you provide a function name at the time of its declaration and its actual definition can be given anywhere else. For example −

Lvalues and Rvalues in C

There are two kinds of expressions in C −

lvalue − Expressions that refer to a memory location are called «lvalue» expressions. An lvalue may appear as either the left-hand or right-hand side of an assignment.

rvalue − The term rvalue refers to a data value that is stored at some address in memory. An rvalue is an expression that cannot have a value assigned to it which means an rvalue may appear on the right-hand side but not on the left-hand side of an assignment.

Variables are lvalues and so they may appear on the left-hand side of an assignment. Numeric literals are rvalues and so they may not be assigned and cannot appear on the left-hand side. Take a look at the following valid and invalid statements −

Constants refer to fixed values that the program may not alter during its execution. These fixed values are also called literals.

Constants can be of any of the basic data types like an integer constant, a floating constant, a character constant, or a string literal. There are enumeration constants as well.

Constants are treated just like regular variables except that their values cannot be modified after their definition.

Integer Literals

An integer literal can be a decimal, octal, or hexadecimal constant. A prefix specifies the base or radix: 0x or 0X for hexadecimal, 0 for octal, and nothing for decimal.

An integer literal can also have a suffix that is a combination of U and L, for unsigned and long, respectively. The suffix can be uppercase or lowercase and can be in any order.

Here are some examples of integer literals −

Following are other examples of various types of integer literals −

Floating-point Literals

A floating-point literal has an integer part, a decimal point, a fractional part, and an exponent part. You can represent floating point literals either in decimal form or exponential form.

While representing decimal form, you must include the decimal point, the exponent, or both; and while representing exponential form, you must include the integer part, the fractional part, or both. The signed exponent is introduced by e or E.

Here are some examples of floating-point literals −

Character Constants

Character literals are enclosed in single quotes, e.g., ‘x’ can be stored in a simple variable of char type.

A character literal can be a plain character (e.g., ‘x’), an escape sequence (e.g., ‘\t’), or a universal character (e.g., ‘\u02C0’).

There are certain characters in C that represent special meaning when preceded by a backslash for example, newline (\n) or tab (\t).

Following is the example to show a few escape sequence characters −

When the above code is compiled and executed, it produces the following result −

String Literals

String literals or constants are enclosed in double quotes «». A string contains characters that are similar to character literals: plain characters, escape sequences, and universal characters.

You can break a long line into multiple lines using string literals and separating them using white spaces.

Here are some examples of string literals. All the three forms are identical strings.

Defining Constants

There are two simple ways in C to define constants −

Using #define preprocessor.

Using const keyword.

The #define Preprocessor

Given below is the form to use #define preprocessor to define a constant −

The following example explains it in detail −

When the above code is compiled and executed, it produces the following result −

The const Keyword

You can use const prefix to declare constants with a specific type as follows −

The following example explains it in detail −

When the above code is compiled and executed, it produces the following result −

Note that it is a good programming practice to define constants in CAPITALS.

A storage class defines the scope (visibility) and life-time of variables and/or functions within a C Program. They precede the type that they modify. We have four different storage classes in a C program −

The auto Storage Class

The auto storage class is the default storage class for all local variables.

The example above defines two variables with in the same storage class. ‘auto’ can only be used within functions, i.e., local variables.

The register Storage Class

The register storage class is used to define local variables that should be stored in a register instead of RAM. This means that the variable has a maximum size equal to the register size (usually one word) and can’t have the unary ‘&’ operator applied to it (as it does not have a memory location).

The register should only be used for variables that require quick access such as counters. It should also be noted that defining ‘register’ does not mean that the variable will be stored in a register. It means that it MIGHT be stored in a register depending on hardware and implementation restrictions.

The static Storage Class

The static storage class instructs the compiler to keep a local variable in existence during the life-time of the program instead of creating and destroying it each time it comes into and goes out of scope. Therefore, making local variables static allows them to maintain their values between function calls.

The static modifier may also be applied to global variables. When this is done, it causes that variable’s scope to be restricted to the file in which it is declared.

In C programming, when static is used on a global variable, it causes only one copy of that member to be shared by all the objects of its class.

When the above code is compiled and executed, it produces the following result −

The extern Storage Class

The extern storage class is used to give a reference of a global variable that is visible to ALL the program files. When you use ‘extern’, the variable cannot be initialized however, it points the variable name at a storage location that has been previously defined.

When you have multiple files and you define a global variable or function, which will also be used in other files, then extern will be used in another file to provide the reference of defined variable or function. Just for understanding, extern is used to declare a global variable or function in another file.

The extern modifier is most commonly used when there are two or more files sharing the same global variables or functions as explained below.

First File: main.c

Second File: support.c

Here, extern is being used to declare count in the second file, where as it has its definition in the first file, main.c. Now, compile these two files as follows −

It will produce the executable program a.out. When this program is executed, it produces the following result −

An operator is a symbol that tells the compiler to perform specific mathematical or logical functions. C language is rich in built-in operators and provides the following types of operators −

We will, in this chapter, look into the way each operator works.

Arithmetic Operators

The following table shows all the arithmetic operators supported by the C language. Assume variable A holds 10 and variable B holds 20 then −

Relational Operators

The following table shows all the relational operators supported by C. Assume variable A holds 10 and variable B holds 20 then −

Assignment Operators

The following table lists the assignment operators supported by the C language −

Misc Operators ↦ sizeof & ternary

Besides the operators discussed above, there are a few other important operators including sizeof and ? : supported by the C Language.

Operators Precedence in C

Operator precedence determines the grouping of terms in an expression and decides how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has a higher precedence than the addition operator.

For example, x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has a higher precedence than +, so it first gets multiplied with 3*2 and then adds into 7.

Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.

We have kept max() along with main() and compiled the source code. While running the final executable, it would produce the following result −

Function Arguments

If a function is to use arguments, it must declare variables that accept the values of the arguments. These variables are called the formal parameters of the function.

Formal parameters behave like other local variables inside the function and are created upon entry into the function and destroyed upon exit.

While calling a function, there are two ways in which arguments can be passed to a function −

Sr.No.	Type & Description
1

Sr.No.

Call Type & Description

Call by value

This method copies the actual value of an argument into the formal parameter of the function. In this case, changes made to the parameter inside the function have no effect on the argument.

This method copies the address of an argument into the formal parameter. Inside the function, the address is used to access the actual argument used in the call. This means that changes made to the parameter affect the argument.

By default, C uses call by value to pass arguments. In general, it means the code within a function cannot alter the arguments used to call the function.

A scope in any programming is a region of the program where a defined variable can have its existence and beyond that variable it cannot be accessed. There are three places where variables can be declared in C programming language −

Inside a function or a block which is called local variables.

Outside of all functions which is called global variables.

In the definition of function parameters which are called formal parameters.

Let us understand what are local and global variables, and formal parameters.

Local Variables

Variables that are declared inside a function or block are called local variables. They can be used only by statements that are inside that function or block of code. Local variables are not known to functions outside their own. The following example shows how local variables are used. Here all the variables a, b, and c are local to main() function.

Global Variables

Global variables are defined outside a function, usually on top of the program. Global variables hold their values throughout the lifetime of your program and they can be accessed inside any of the functions defined for the program.

A global variable can be accessed by any function. That is, a global variable is available for use throughout your entire program after its declaration. The following program show how global variables are used in a program.

A program can have same name for local and global variables but the value of local variable inside a function will take preference. Here is an example −

When the above code is compiled and executed, it produces the following result −

Formal Parameters

Formal parameters, are treated as local variables with-in a function and they take precedence over global variables. Following is an example −

When the above code is compiled and executed, it produces the following result −

Initializing Local and Global Variables

When a local variable is defined, it is not initialized by the system, you must initialize it yourself. Global variables are initialized automatically by the system when you define them as follows −

Data Type	Initial Default Value
int	0
char	‘\0’
float	0
double	0
pointer	NULL

It is a good programming practice to initialize variables properly, otherwise your program may produce unexpected results, because uninitialized variables will take some garbage value already available at their memory location.

Arrays a kind of data structure that can store a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

All arrays consist of contiguous memory locations. The lowest address corresponds to the first element and the highest address to the last element.

Declaring Arrays

To declare an array in C, a programmer specifies the type of the elements and the number of elements required by an array as follows −

This is called a single-dimensional array. The arraySize must be an integer constant greater than zero and type can be any valid C data type. For example, to declare a 10-element array called balance of type double, use this statement −

Here balance is a variable array which is sufficient to hold up to 10 double numbers.

Initializing Arrays

You can initialize an array in C either one by one or using a single statement as follows −

The number of values between braces < >cannot be larger than the number of elements that we declare for the array between square brackets [ ].

If you omit the size of the array, an array just big enough to hold the initialization is created. Therefore, if you write −

You will create exactly the same array as you did in the previous example. Following is an example to assign a single element of the array −

The above statement assigns the 5 th element in the array with a value of 50.0. All arrays have 0 as the index of their first element which is also called the base index and the last index of an array will be total size of the array minus 1. Shown below is the pictorial representation of the array we discussed above −

Accessing Array Elements

An element is accessed by indexing the array name. This is done by placing the index of the element within square brackets after the name of the array. For example −

The above statement will take the 10 th element from the array and assign the value to salary variable. The following example Shows how to use all the three above mentioned concepts viz. declaration, assignment, and accessing arrays −

When the above code is compiled and executed, it produces the following result −

Arrays in Detail

Arrays are important to C and should need a lot more attention. The following important concepts related to array should be clear to a C programmer −

Sr.No.

Concept & Description

Multi-dimensional arrays

C supports multidimensional arrays. The simplest form of the multidimensional array is the two-dimensional array.

You can pass to the function a pointer to an array by specifying the array’s name without an index.

C allows a function to return an array.

You can generate a pointer to the first element of an array by simply specifying the array name, without any index.

Pointers in C are easy and fun to learn. Some C programming tasks are performed more easily with pointers, and other tasks, such as dynamic memory allocation, cannot be performed without using pointers. So it becomes necessary to learn pointers to become a perfect C programmer. Let’s start learning them in simple and easy steps.

As you know, every variable is a memory location and every memory location has its address defined which can be accessed using ampersand (&) operator, which denotes an address in memory. Consider the following example, which prints the address of the variables defined −

When the above code is compiled and executed, it produces the following result −

What are Pointers?

A pointer is a variable whose value is the address of another variable, i.e., direct address of the memory location. Like any variable or constant, you must declare a pointer before using it to store any variable address. The general form of a pointer variable declaration is −

Here, type is the pointer’s base type; it must be a valid C data type and var-name is the name of the pointer variable. The asterisk * used to declare a pointer is the same asterisk used for multiplication. However, in this statement the asterisk is being used to designate a variable as a pointer. Take a look at some of the valid pointer declarations −

The actual data type of the value of all pointers, whether integer, float, character, or otherwise, is the same, a long hexadecimal number that represents a memory address. The only difference between pointers of different data types is the data type of the variable or constant that the pointer points to.

How to Use Pointers?

There are a few important operations, which we will do with the help of pointers very frequently. (a) We define a pointer variable, (b) assign the address of a variable to a pointer and (c) finally access the value at the address available in the pointer variable. This is done by using unary operator * that returns the value of the variable located at the address specified by its operand. The following example makes use of these operations −

When the above code is compiled and executed, it produces the following result −

NULL Pointers

It is always a good practice to assign a NULL value to a pointer variable in case you do not have an exact address to be assigned. This is done at the time of variable declaration. A pointer that is assigned NULL is called a null pointer.

The NULL pointer is a constant with a value of zero defined in several standard libraries. Consider the following program −

When the above code is compiled and executed, it produces the following result −

In most of the operating systems, programs are not permitted to access memory at address 0 because that memory is reserved by the operating system. However, the memory address 0 has special significance; it signals that the pointer is not intended to point to an accessible memory location. But by convention, if a pointer contains the null (zero) value, it is assumed to point to nothing.

To check for a null pointer, you can use an ‘if’ statement as follows −

Pointers in Detail

Pointers have many but easy concepts and they are very important to C programming. The following important pointer concepts should be clear to any C programmer −

Sr.No.

Concept & Description

Pointer arithmetic

You can define arrays to hold a number of pointers.

C allows you to have pointer on a pointer and so on.

Passing an argument by reference or by address enable the passed argument to be changed in the calling function by the called function.

C allows a function to return a pointer to the local variable, static variable, and dynamically allocated memory as well.

Strings are actually one-dimensional array of characters terminated by a null character ‘\0’. Thus a null-terminated string contains the characters that comprise the string followed by a null.

The following declaration and initialization create a string consisting of the word «Hello». To hold the null character at the end of the array, the size of the character array containing the string is one more than the number of characters in the word «Hello.»

If you follow the rule of array initialization then you can write the above statement as follows −

Following is the memory presentation of the above defined string in C/C++ −

Actually, you do not place the null character at the end of a string constant. The C compiler automatically places the ‘\0’ at the end of the string when it initializes the array. Let us try to print the above mentioned string −

When the above code is compiled and executed, it produces the following result −

C supports a wide range of functions that manipulate null-terminated strings −

Copies string s2 into string s1.

Concatenates string s2 onto the end of string s1.

Returns the length of string s1.

Returns 0 if s1 and s2 are the same; less than 0 if s1 s2.

Returns a pointer to the first occurrence of character ch in string s1.

Returns a pointer to the first occurrence of string s2 in string s1.

The following example uses some of the above-mentioned functions −

When the above code is compiled and executed, it produces the following result −

Arrays allow to define type of variables that can hold several data items of the same kind. Similarly structure is another user defined data type available in C that allows to combine data items of different kinds.

Structures are used to represent a record. Suppose you want to keep track of your books in a library. You might want to track the following attributes about each book −

Defining a Structure

To define a structure, you must use the struct statement. The struct statement defines a new data type, with more than one member. The format of the struct statement is as follows −

The structure tag is optional and each member definition is a normal variable definition, such as int i; or float f; or any other valid variable definition. At the end of the structure’s definition, before the final semicolon, you can specify one or more structure variables but it is optional. Here is the way you would declare the Book structure −

Accessing Structure Members

To access any member of a structure, we use the member access operator (.). The member access operator is coded as a period between the structure variable name and the structure member that we wish to access. You would use the keyword struct to define variables of structure type. The following example shows how to use a structure in a program −

When the above code is compiled and executed, it produces the following result −

Structures as Function Arguments

You can pass a structure as a function argument in the same way as you pass any other variable or pointer.

When the above code is compiled and executed, it produces the following result −

Pointers to Structures

You can define pointers to structures in the same way as you define pointer to any other variable −

Now, you can store the address of a structure variable in the above defined pointer variable. To find the address of a structure variable, place the ‘&amp’; operator before the structure’s name as follows −

To access the members of a structure using a pointer to that structure, you must use the → operator as follows −

Let us re-write the above example using structure pointer.

When the above code is compiled and executed, it produces the following result −

Bit Fields

Bit Fields allow the packing of data in a structure. This is especially useful when memory or data storage is at a premium. Typical examples include −

Packing several objects into a machine word. e.g. 1 bit flags can be compacted.

C allows us to do this in a structure definition by putting :bit length after the variable. For example −

Here, the packed_struct contains 6 members: Four 1 bit flags f1..f3, a 4-bit type and a 9-bit my_int.

C automatically packs the above bit fields as compactly as possible, provided that the maximum length of the field is less than or equal to the integer word length of the computer. If this is not the case, then some compilers may allow memory overlap for the fields while others would store the next field in the next word.

A union is a special data type available in C that allows to store different data types in the same memory location. You can define a union with many members, but only one member can contain a value at any given time. Unions provide an efficient way of using the same memory location for multiple-purpose.

Defining a Union

To define a union, you must use the union statement in the same way as you did while defining a structure. The union statement defines a new data type with more than one member for your program. The format of the union statement is as follows −

The union tag is optional and each member definition is a normal variable definition, such as int i; or float f; or any other valid variable definition. At the end of the union’s definition, before the final semicolon, you can specify one or more union variables but it is optional. Here is the way you would define a union type named Data having three members i, f, and str −

Now, a variable of Data type can store an integer, a floating-point number, or a string of characters. It means a single variable, i.e., same memory location, can be used to store multiple types of data. You can use any built-in or user defined data types inside a union based on your requirement.

The memory occupied by a union will be large enough to hold the largest member of the union. For example, in the above example, Data type will occupy 20 bytes of memory space because this is the maximum space which can be occupied by a character string. The following example displays the total memory size occupied by the above union −

When the above code is compiled and executed, it produces the following result −

Accessing Union Members

To access any member of a union, we use the member access operator (.). The member access operator is coded as a period between the union variable name and the union member that we wish to access. You would use the keyword union to define variables of union type. The following example shows how to use unions in a program −

When the above code is compiled and executed, it produces the following result −

Here, we can see that the values of i and f members of union got corrupted because the final value assigned to the variable has occupied the memory location and this is the reason that the value of str member is getting printed very well.

Now let’s look into the same example once again where we will use one variable at a time which is the main purpose of having unions −

When the above code is compiled and executed, it produces the following result −

Here, all the members are getting printed very well because one member is being used at a time.

Suppose your C program contains a number of TRUE/FALSE variables grouped in a structure called status, as follows −

This structure requires 8 bytes of memory space but in actual, we are going to store either 0 or 1 in each of the variables. The C programming language offers a better way to utilize the memory space in such situations.

If you are using such variables inside a structure then you can define the width of a variable which tells the C compiler that you are going to use only those number of bytes. For example, the above structure can be re-written as follows −

The above structure requires 4 bytes of memory space for status variable, but only 2 bits will be used to store the values.

If you will use up to 32 variables each one with a width of 1 bit, then also the status structure will use 4 bytes. However as soon as you have 33 variables, it will allocate the next slot of the memory and it will start using 8 bytes. Let us check the following example to understand the concept −

When the above code is compiled and executed, it produces the following result −

Bit Field Declaration

The declaration of a bit-field has the following form inside a structure −

The following table describes the variable elements of a bit field −

Sr.No.	Function & Purpose
1

An integer type that determines how a bit-field’s value is interpreted. The type may be int, signed int, or unsigned int.

The name of the bit-field.

The number of bits in the bit-field. The width must be less than or equal to the bit width of the specified type.

The variables defined with a predefined width are called bit fields. A bit field can hold more than a single bit; for example, if you need a variable to store a value from 0 to 7, then you can define a bit field with a width of 3 bits as follows −

The above structure definition instructs the C compiler that the age variable is going to use only 3 bits to store the value. If you try to use more than 3 bits, then it will not allow you to do so. Let us try the following example −

When the above code is compiled it will compile with a warning and when executed, it produces the following result −

The C programming language provides a keyword called typedef, which you can use to give a type a new name. Following is an example to define a term BYTE for one-byte numbers −

After this type definition, the identifier BYTE can be used as an abbreviation for the type unsigned char, for example..

By convention, uppercase letters are used for these definitions to remind the user that the type name is really a symbolic abbreviation, but you can use lowercase, as follows −

You can use typedef to give a name to your user defined data types as well. For example, you can use typedef with structure to define a new data type and then use that data type to define structure variables directly as follows −

When the above code is compiled and executed, it produces the following result −

typedef vs #define

#define is a C-directive which is also used to define the aliases for various data types similar to typedef but with the following differences −

typedef is limited to giving symbolic names to types only where as #define can be used to define alias for values as well, q., you can define 1 as ONE etc.

typedef interpretation is performed by the compiler whereas #define statements are processed by the pre-processor.

The following example shows how to use #define in a program −

When the above code is compiled and executed, it produces the following result −

When we say Input, it means to feed some data into a program. An input can be given in the form of a file or from the command line. C programming provides a set of built-in functions to read the given input and feed it to the program as per requirement.

When we say Output, it means to display some data on screen, printer, or in any file. C programming provides a set of built-in functions to output the data on the computer screen as well as to save it in text or binary files.

The Standard Files

C programming treats all the devices as files. So devices such as the display are addressed in the same way as files and the following three files are automatically opened when a program executes to provide access to the keyboard and screen.

Sr.No.	Element & Description
1

Standard File	File Pointer	Device
Standard input	stdin	Keyboard
Standard output	stdout	Screen
Standard error	stderr	Your screen

The file pointers are the means to access the file for reading and writing purpose. This section explains how to read values from the screen and how to print the result on the screen.

The getchar() and putchar() Functions

The int getchar(void) function reads the next available character from the screen and returns it as an integer. This function reads only single character at a time. You can use this method in the loop in case you want to read more than one character from the screen.

The int putchar(int c) function puts the passed character on the screen and returns the same character. This function puts only single character at a time. You can use this method in the loop in case you want to display more than one character on the screen. Check the following example −

When the above code is compiled and executed, it waits for you to input some text. When you enter a text and press enter, then the program proceeds and reads only a single character and displays it as follows −

The gets() and puts() Functions

The char *gets(char *s) function reads a line from stdin into the buffer pointed to by s until either a terminating newline or EOF (End of File).

The int puts(const char *s) function writes the string ‘s’ and ‘a’ trailing newline to stdout.

NOTE: Though it has been deprecated to use gets() function, Instead of using gets, you want to use fgets().

When the above code is compiled and executed, it waits for you to input some text. When you enter a text and press enter, then the program proceeds and reads the complete line till end, and displays it as follows −

The scanf() and printf() Functions

The format can be a simple constant string, but you can specify %s, %d, %c, %f, etc., to print or read strings, integer, character or float respectively. There are many other formatting options available which can be used based on requirements. Let us now proceed with a simple example to understand the concepts better −

When the above code is compiled and executed, it waits for you to input some text. When you enter a text and press enter, then program proceeds and reads the input and displays it as follows −

Here, it should be noted that scanf() expects input in the same format as you provided %s and %d, which means you have to provide valid inputs like «string integer». If you provide «string string» or «integer integer», then it will be assumed as wrong input. Secondly, while reading a string, scanf() stops reading as soon as it encounters a space, so «this is test» are three strings for scanf().

The last chapter explained the standard input and output devices handled by C programming language. This chapter cover how C programmers can create, open, close text or binary files for their data storage.

A file represents a sequence of bytes, regardless of it being a text file or a binary file. C programming language provides access on high level functions as well as low level (OS level) calls to handle file on your storage devices. This chapter will take you through the important calls for file management.

Opening Files

You can use the fopen( ) function to create a new file or to open an existing file. This call will initialize an object of the type FILE, which contains all the information necessary to control the stream. The prototype of this function call is as follows −

Here, filename is a string literal, which you will use to name your file, and access mode can have one of the following values −

Opens an existing text file for reading purpose.

Opens a text file for writing. If it does not exist, then a new file is created. Here your program will start writing content from the beginning of the file.

Opens a text file for writing in appending mode. If it does not exist, then a new file is created. Here your program will start appending content in the existing file content.

Opens a text file for both reading and writing.

Opens a text file for both reading and writing. It first truncates the file to zero length if it exists, otherwise creates a file if it does not exist.

Opens a text file for both reading and writing. It creates the file if it does not exist. The reading will start from the beginning but writing can only be appended.

If you are going to handle binary files, then you will use following access modes instead of the above mentioned ones −

Closing a File

To close a file, use the fclose( ) function. The prototype of this function is −

The fclose(-) function returns zero on success, or EOF if there is an error in closing the file. This function actually flushes any data still pending in the buffer to the file, closes the file, and releases any memory used for the file. The EOF is a constant defined in the header file stdio.h.

There are various functions provided by C standard library to read and write a file, character by character, or in the form of a fixed length string.

Writing a File

Following is the simplest function to write individual characters to a stream −

The function fputc() writes the character value of the argument c to the output stream referenced by fp. It returns the written character written on success otherwise EOF if there is an error. You can use the following functions to write a null-terminated string to a stream −

Make sure you have /tmp directory available. If it is not, then before proceeding, you must create this directory on your machine.

When the above code is compiled and executed, it creates a new file test.txt in /tmp directory and writes two lines using two different functions. Let us read this file in the next section.

Reading a File

Given below is the simplest function to read a single character from a file −

The fgetc() function reads a character from the input file referenced by fp. The return value is the character read, or in case of any error, it returns EOF. The following function allows to read a string from a stream −

The functions fgets() reads up to n-1 characters from the input stream referenced by fp. It copies the read string into the buffer buf, appending a null character to terminate the string.

When the above code is compiled and executed, it reads the file created in the previous section and produces the following result −

Let’s see a little more in detail about what happened here. First, fscanf() read just This because after that, it encountered a space, second call is for fgets() which reads the remaining line till it encountered end of line. Finally, the last call fgets() reads the second line completely.

Binary I/O Functions

There are two functions, that can be used for binary input and output −

The C Preprocessor is not a part of the compiler, but is a separate step in the compilation process. In simple terms, a C Preprocessor is just a text substitution tool and it instructs the compiler to do required pre-processing before the actual compilation. We’ll refer to the C Preprocessor as CPP.

All preprocessor commands begin with a hash symbol (#). It must be the first nonblank character, and for readability, a preprocessor directive should begin in the first column. The following section lists down all the important preprocessor directives −

Sr.No.	Mode & Description
1

Substitutes a preprocessor macro.

Inserts a particular header from another file.

Undefines a preprocessor macro.

Returns true if this macro is defined.

Returns true if this macro is not defined.

Tests if a compile time condition is true.

The alternative for #if.

#else and #if in one statement.

Ends preprocessor conditional.

Prints error message on stderr.

Issues special commands to the compiler, using a standardized method.

Preprocessors Examples

Analyze the following examples to understand various directives.

This directive tells the CPP to replace instances of MAX_ARRAY_LENGTH with 20. Use #define for constants to increase readability.

These directives tell the CPP to get stdio.h from System Libraries and add the text to the current source file. The next line tells CPP to get myheader.h from the local directory and add the content to the current source file.

It tells the CPP to undefine existing FILE_SIZE and define it as 42.

It tells the CPP to define MESSAGE only if MESSAGE isn’t already defined.

It tells the CPP to process the statements enclosed if DEBUG is defined. This is useful if you pass the -DDEBUG flag to the gcc compiler at the time of compilation. This will define DEBUG, so you can turn debugging on and off on the fly during compilation.

Predefined Macros

ANSI C defines a number of macros. Although each one is available for use in programming, the predefined macros should not be directly modified.

Sr.No.	Directive & Description
1

The current date as a character literal in «MMM DD YYYY» format.

The current time as a character literal in «HH:MM:SS» format.

This contains the current filename as a string literal.

This contains the current line number as a decimal constant.

Defined as 1 when the compiler complies with the ANSI standard.

Let’s try the following example −

When the above code in a file test.c is compiled and executed, it produces the following result −

Preprocessor Operators

The C preprocessor offers the following operators to help create macros −

The Macro Continuation (\) Operator

A macro is normally confined to a single line. The macro continuation operator (\) is used to continue a macro that is too long for a single line. For example −

The Stringize (#) Operator

The stringize or number-sign operator ( ‘#’ ), when used within a macro definition, converts a macro parameter into a string constant. This operator may be used only in a macro having a specified argument or parameter list. For example −

When the above code is compiled and executed, it produces the following result −

The Token Pasting (##) Operator

The token-pasting operator (##) within a macro definition combines two arguments. It permits two separate tokens in the macro definition to be joined into a single token. For example −

When the above code is compiled and executed, it produces the following result −

It happened so because this example results in the following actual output from the preprocessor −

This example shows the concatenation of token##n into token34 and here we have used both stringize and token-pasting.

The Defined() Operator

The preprocessor defined operator is used in constant expressions to determine if an identifier is defined using #define. If the specified identifier is defined, the value is true (non-zero). If the symbol is not defined, the value is false (zero). The defined operator is specified as follows −

When the above code is compiled and executed, it produces the following result −

Parameterized Macros

One of the powerful functions of the CPP is the ability to simulate functions using parameterized macros. For example, we might have some code to square a number as follows −

We can rewrite above the code using a macro as follows −

Macros with arguments must be defined using the #define directive before they can be used. The argument list is enclosed in parentheses and must immediately follow the macro name. Spaces are not allowed between the macro name and open parenthesis. For example −

When the above code is compiled and executed, it produces the following result −

A header file is a file with extension .h which contains C function declarations and macro definitions to be shared between several source files. There are two types of header files: the files that the programmer writes and the files that comes with your compiler.

You request to use a header file in your program by including it with the C preprocessing directive #include, like you have seen inclusion of stdio.h header file, which comes along with your compiler.

Including a header file is equal to copying the content of the header file but we do not do it because it will be error-prone and it is not a good idea to copy the content of a header file in the source files, especially if we have multiple source files in a program.

A simple practice in C or C++ programs is that we keep all the constants, macros, system wide global variables, and function prototypes in the header files and include that header file wherever it is required.

Include Syntax

Both the user and the system header files are included using the preprocessing directive #include. It has the following two forms −

Include Operation

The #include directive works by directing the C preprocessor to scan the specified file as input before continuing with the rest of the current source file. The output from the preprocessor contains the output already generated, followed by the output resulting from the included file, followed by the output that comes from the text after the #include directive. For example, if you have a header file header.h as follows −

and a main program called program.c that uses the header file, like this −

the compiler will see the same token stream as it would if program.c read.

Once-Only Headers

If a header file happens to be included twice, the compiler will process its contents twice and it will result in an error. The standard way to prevent this is to enclose the entire real contents of the file in a conditional, like this −

This construct is commonly known as a wrapper #ifndef. When the header is included again, the conditional will be false, because HEADER_FILE is defined. The preprocessor will skip over the entire contents of the file, and the compiler will not see it twice.

Computed Includes

Sometimes it is necessary to select one of the several different header files to be included into your program. For instance, they might specify configuration parameters to be used on different sorts of operating systems. You could do this with a series of conditionals as follows −

But as it grows, it becomes tedious, instead the preprocessor offers the ability to use a macro for the header name. This is called a computed include. Instead of writing a header name as the direct argument of #include, you simply put a macro name there −

Type casting is a way to convert a variable from one data type to another data type. For example, if you want to store a ‘long’ value into a simple integer then you can type cast ‘long’ to ‘int’. You can convert the values from one type to another explicitly using the cast operator as follows −

Consider the following example where the cast operator causes the division of one integer variable by another to be performed as a floating-point operation −

When the above code is compiled and executed, it produces the following result −

It should be noted here that the cast operator has precedence over division, so the value of sum is first converted to type double and finally it gets divided by count yielding a double value.

Type conversions can be implicit which is performed by the compiler automatically, or it can be specified explicitly through the use of the cast operator. It is considered good programming practice to use the cast operator whenever type conversions are necessary.

Integer Promotion

Integer promotion is the process by which values of integer type «smaller» than int or unsigned int are converted either to int or unsigned int. Consider an example of adding a character with an integer −

When the above code is compiled and executed, it produces the following result −

Here, the value of sum is 116 because the compiler is doing integer promotion and converting the value of ‘c’ to ASCII before performing the actual addition operation.

Usual Arithmetic Conversion

The usual arithmetic conversions are implicitly performed to cast their values to a common type. The compiler first performs integer promotion; if the operands still have different types, then they are converted to the type that appears highest in the following hierarchy −

The usual arithmetic conversions are not performed for the assignment operators, nor for the logical operators && and ||. Let us take the following example to understand the concept −

When the above code is compiled and executed, it produces the following result −

Here, it is simple to understand that first c gets converted to integer, but as the final value is double, usual arithmetic conversion applies and the compiler converts i and c into ‘float’ and adds them yielding a ‘float’ result.

So a C programmer can check the returned values and can take appropriate action depending on the return value. It is a good practice, to set errno to 0 at the time of initializing a program. A value of 0 indicates that there is no error in the program.

errno, perror(). and strerror()

The C programming language provides perror() and strerror() functions which can be used to display the text message associated with errno.

The perror() function displays the string you pass to it, followed by a colon, a space, and then the textual representation of the current errno value.

The strerror() function, which returns a pointer to the textual representation of the current errno value.

Let’s try to simulate an error condition and try to open a file which does not exist. Here I’m using both the functions to show the usage, but you can use one or more ways of printing your errors. Second important point to note is that you should use stderr file stream to output all the errors.

When the above code is compiled and executed, it produces the following result −

Divide by Zero Errors

It is a common problem that at the time of dividing any number, programmers do not check if a divisor is zero and finally it creates a runtime error.

The code below fixes this by checking if the divisor is zero before dividing −

When the above code is compiled and executed, it produces the following result −

Program Exit Status

It is a common practice to exit with a value of EXIT_SUCCESS in case of program coming out after a successful operation. Here, EXIT_SUCCESS is a macro and it is defined as 0.

When the above code is compiled and executed, it produces the following result −

Recursion is the process of repeating items in a self-similar way. In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.

The C programming language supports recursion, i.e., a function to call itself. But while using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.

Recursive functions are very useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc.

Number Factorial

The following example calculates the factorial of a given number using a recursive function −

When the above code is compiled and executed, it produces the following result −

Fibonacci Series

The following example generates the Fibonacci series for a given number using a recursive function −

When the above code is compiled and executed, it produces the following result −

Sometimes, you may come across a situation, when you want to have a function, which can take variable number of arguments, i.e., parameters, instead of predefined number of parameters. The C programming language provides a solution for this situation and you are allowed to define a function which can accept variable number of parameters based on your requirement. The following example shows the definition of such a function.

It should be noted that the function func() has its last argument as ellipses, i.e. three dotes (. ) and the one just before the ellipses is always an int which will represent the total number variable arguments passed. To use such functionality, you need to make use of stdarg.h header file which provides the functions and macros to implement the functionality of variable arguments and follow the given steps −

Define a function with its last parameter as ellipses and the one just before the ellipses is always an int which will represent the number of arguments.

Create a va_list type variable in the function definition. This type is defined in stdarg.h header file.

Use int parameter and va_start macro to initialize the va_list variable to an argument list. The macro va_start is defined in stdarg.h header file.

Use va_arg macro and va_list variable to access each item in argument list.

Use a macro va_end to clean up the memory assigned to va_list variable.

Now let us follow the above steps and write down a simple function which can take the variable number of parameters and return their average −

When the above code is compiled and executed, it produces the following result. It should be noted that the function average() has been called twice and each time the first argument represents the total number of variable arguments being passed. Only ellipses will be used to pass variable number of arguments.

This chapter explains dynamic memory management in C. The C programming language provides several functions for memory allocation and management. These functions can be found in the header file.

Sr.No.	Macro & Description
1

void *calloc(int num, int size);

This function allocates an array of num elements each of which size in bytes will be size.

void free(void *address);

This function releases a block of memory block specified by address.

void *malloc(size_t size);

This function allocates an array of num bytes and leave them uninitialized.

void *realloc(void *address, int newsize);

This function re-allocates memory extending it upto newsize.

Allocating Memory Dynamically

While programming, if you are aware of the size of an array, then it is easy and you can define it as an array. For example, to store a name of any person, it can go up to a maximum of 100 characters, so you can define something as follows −

But now let us consider a situation where you have no idea about the length of the text you need to store, for example, you want to store a detailed description about a topic. Here we need to define a pointer to character without defining how much memory is required and later, based on requirement, we can allocate memory as shown in the below example −

When the above code is compiled and executed, it produces the following result.

Same program can be written using calloc(); only thing is you need to replace malloc with calloc as follows −

So you have complete control and you can pass any size value while allocating memory, unlike arrays where once the size defined, you cannot change it.

Resizing and Releasing Memory

When your program comes out, operating system automatically release all the memory allocated by your program but as a good practice when you are not in need of memory anymore then you should release that memory by calling the function free().

Alternatively, you can increase or decrease the size of an allocated memory block by calling the function realloc(). Let us check the above program once again and make use of realloc() and free() functions −

When the above code is compiled and executed, it produces the following result.

You can try the above example without re-allocating extra memory, and strcat() function will give an error due to lack of available memory in description.

It is possible to pass some values from the command line to your C programs when they are executed. These values are called command line arguments and many times they are important for your program especially when you want to control your program from outside instead of hard coding those values inside the code.

The command line arguments are handled using main() function arguments where argc refers to the number of arguments passed, and argv[] is a pointer array which points to each argument passed to the program. Following is a simple example which checks if there is any argument supplied from the command line and take action accordingly −

When the above code is compiled and executed with single argument, it produces the following result.

When the above code is compiled and executed with a two arguments, it produces the following result.

When the above code is compiled and executed without passing any argument, it produces the following result.

It should be noted that argv[0] holds the name of the program itself and argv[1] is a pointer to the first command line argument supplied, and *argv[n] is the last argument. If no arguments are supplied, argc will be one, and if you pass one argument then argc is set at 2.

You pass all the command line arguments separated by a space, but if argument itself has a space then you can pass such arguments by putting them inside double quotes «» or single quotes ». Let us re-write above example once again where we will print program name and we also pass a command line argument by putting inside double quotes −

When the above code is compiled and executed with a single argument separated by space but inside double quotes, it produces the following result.

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Sr.No.	Function & Description
1