Variables, constants and data types in C#

In this tutorial you will learn about variables, constants and data types in the C# language.

Variables are like containers that can store data that you will use in your application. Variables can be given a value to store that can be accessed and modified or updated throughout the program whereas constants are given a value that can’t be changed in another part of the program – in other words the variable’s value is constant throughout the program.

Variables and constants must be given a unique name (starting with lowercase letter and cannot contain spaces or special characters) and they must have a certain type. A type specifies the kind of data that a variable can hold. A variable that has a name and a type can then have a value assigned to it.

Take a look at the following line of code:

int myNumber = 5;

The line of code above says that a new variable called myNumber is being declared. It is of the int (integer) type and is assigned a value of 5.

The table below shows the data types available in the C# language.

Type Description
int The integer data type stores positive or negative whole numbers eg. 5
float The float data type stores floating point numbers (numbers with decimal places).
double The double data type stores floating point numbers but with double precision.
bool The bool (short for Boolean) data type stores true or false values only eg. true
char The char data type stores a single character such as a letter, number, space or special character (eg. a, 1, !).  A char value is written in single quotes eg. ‘a’.
string The string data type stores letters, numbers and other characters in the form of words or sentences. A string value is written inside double quotes eg. “Hello World”.

Watch the video below and then scroll down for the sample code.

Sample code

using System;

namespace MyCSharpProject
  class MainClass
    public static void Main(string[] args)
      const string mySentence = "The quick brown fox jumps over the lazy dog.";

      int myNumber = 5;

      float myFloat = 15.279f;

      double myDouble = 150.24649;

      bool myBool = false;


Next tutorial: Arithmetic and assignment operators