First program line by line

Our first program is listed below:

class Program
{
    static void Main(string[] args)
    {
        int i = 0;
        int j = 2;
        
        System.Console.WriteLine("i=" + i);
        System.Console.WriteLine("j=" + j);
    }
}

The heart of the program has four lines of code:

        int i = 0;
        int j = 2;
        
        System.Console.WriteLine("i=" + i);
        System.Console.WriteLine("j=" + j);

It defines two variables, assigns the values and output the content of the variables.

A function groups a series of statements. The following code defines a function.

static void Main(string[] args)

We can rewrite the program as follows:

using System; // Here is the change

class Program
{
    static void Main(string[] args)
    {
        int i = 0;
        int j = 2;
        
        Console.WriteLine("i=" + i);
        Console.WriteLine("j=" + j);
    }
}

The program starts with a using directive that references the System namespace.

Namespaces provide a hierarchical means of organizing C# programs and libraries.

After importing the namespace we don't need to reference the Console class with its full qualified name.

The Main method is declared with the static modifier.

By convention, a static method named Main serves as the entry point of a program.