C++ Variable

  • A variable is a data name given to a data value stored in the memory.
  • The value of variable can vary at the time of execution.
  • Name of the variable should be meaningful and in C++ there are some rules are defined for naming variables which are as follows:

Rules for naming variable

  • Variable name may contain letters, digits and underscore (_) character.
  • The variable name can begin with the letters as well as with underscore (_) character.
  • A variable name should not start with digit.
  • A variable name cannot contain punctuation characters like (@,#,$,%,^,&,* etc)

  • A variable name cannot be a keyword.
  • The variable names may be a combination of uppercase and lowercase characters. For example name and naME are not the same. Both are different.

Declaration of Variables

  • We must declare the variable before using it into the program.
  • A variable is declared using a data type and a meaningful variable name. The basic syntax of variable declaration is as follows:
  • Data_type variable_name;
  • A variable can be of any data type like int, float, double and char etc.
  • Here are some examples of variable declaration:
  • int age;

    float area;

    char m;

    int a,b,c;/*More than one variable of same type can be declare in single statement.*/

    Initializing Variables

  • Variable can be initialized using the assignment operator '='.
  • Variable declaration and initialization can also be performed in same line.
  • The basic syntax to initialize a variable is as follows:
  • variable_name=data_value;

    ----OR-----

    Data_type variable_name=data_value;
  • Here is an example of variable initialization:
  • int x;

    x=3;

    ----OR----

    int x=3;
  • Here is an example of using variable in C++ program:
  • Example

    #include<iostream.h>

    int main()

    {

    int a;/*Variable declaration*/

    a=5;/*Variable initialization*/

    cout<<"\nvalue of a is:"<<a;

    return 0;

    }
  • The output of the above program is as follows:
  • Output

    value of a is:5