C# 0 The Complete Reference

A Second Simple Program

Perhaps no other construct is as important to a programming language as the variable. A 

variable

 is a named memory location that can be assigned a value. It is called a variable 

because its value can be changed during the execution of a program. In other words, the 

content of a variable is changeable, not fixed.

The following program creates two variables called 

x

 and 

y

.

// This program demonstrates variables.

using System;

class Example2 {

  static void Main() {

    int x; // this declares a variable

    int y; // this declares another variable

    x = 100; // this assigns 100 to x

    Console.WriteLine("x contains " + x);

    y = x / 2;

    Console.Write("y contains x / 2: ");

    Console.WriteLine(y);

  }

}

When you run this program, you will see the following output:

x contains 100

y contains x / 2: 50

This program introduces several new concepts. First, the statement

int x; // this declares a variable

declares a variable called 

x

 of type integer. In C#, all variables must be declared before they 

are used. Further, the kind of values that the variable can hold must also be specified. This 

is called the 

type

 of the variable. In this case, 

x

 can hold integer values. These are whole 

www.freepdf-books.com

---

24

 

P a r t   I :  

T h e   C #   L a n g u a g e

numbers. In C#, to declare a variable to be of type integer, precede its name with the 

keyword