A variable defines a location in the memory that holds a value which can be modified later.

   type variable_list;

In the above syntax "type" refers to any one of the C++ data types.

Variables in C++ should be declared before they are used in the code block. It is better to declare it right at the place where its used as this makes the programming much easier. This kind of declaration reduces the errors in the program.

   #include <iostream.h>
   void main()
    {
    int n = 10;
    cout << "Integer value is:"<< n << '\n';
    }	

In the above example "n" is an integer variable declared using return type "int".

Variables can also be intialized dynamically at the place of declaration using the expression as below.

   float area = 3.14159 * rad * rad

In the above example the variable "area" is declared dynamically when it is used.

• Always the first character of a variable must be a letter or an underscore.
• The variable name cannot start with a digit.
• Other characters should be either letters, digits, underscores.
• There is no limit for the length of variables.
• Declared keywords cannot be used as a variable name.
• Upper and lower case letters are distinct.