First Steps in Programming with C# for Beginners

In this lesson we shall learn how to write simple commands and simple programs in C#.

To "program" means to give commands to the computer, e.g.

• Console.WriteLine("Welcome to coding");

The commands are lined up one after another, into a computer program.

Programs are written in a programming language, e.g. C#, Java, JavaScript, Python, PHP, C, C++, Swift, Go, …

Sample C# program (sequence of C# commands):

• var size = 5;

• Console.WriteLine("Size = " + size);

• Console.WriteLine("Area = " + size * size);

We shall learn about programming languages, compilers and interpreters, why we need them and how to use the C# and .NET Core development tools.

We shall introduce Visual Studio and using an Integrated Development Environment (IDE).

In this lesson, we shall create, compile and run a simple "Hello World" C# program in Visual Studio.

We will start Visual Studio (VS), create a new console application project in C#, will edit the source code of the application from the VS code editor, will compile and run the application (using the [Ctrl+F5] key) and will see the produced output on the black console.

We shall send for a very first time our source code for evaluation in the Judge system.

This lesson is about reading numbers from the console using Console.ReadLine() and int.Parse().

Reading in integer number:

• var num = int.Parse(Console.ReadLine());

• In C#, when printing a text, numbers and other data on the console, we can join them by using templates {0}, {1}, {2} etc. In programming, these templates are called placeholders. This is a simple example:

• Console.WriteLine("{0} + {1} = {2}", 3, 5, 3+5);

• In this lesson we shall learn how to use simple checks if conditions

• And If-else conditions:

• In this lesson we shall learn how to use for-loop to repeat a piece of code several times.

• In programming, we often have to execute a block of code several times. For that purpose, we use for-loop. This example repeats a block of code 10 times:

• for (var i = 1; i <= 10; i++)

• {

•     Console.WriteLine("i = " + i);

• }

  
  

In this lesson we shall explain the concepts of nested loops (loops inside another loops) and when and how to use them.

Nested loop == a loop that holds another loop in its body.

• The two loops iterate over different variables.

Example: outer loop (by row) and inner loop (by col)

• for (var row = 1; row <= n; row++)

• {

•    for (var col = 1; col <= n; col++)

•       Console.Write("*");

•    Console.WriteLine();

• }

The above code demonstrates how to use loop in a loop.