Variables are memory locations(storage areas) in the C programming language.

The primary purpose of variables is to store data in memory for later use. Unlike constants which do not change during the program execution, the value of a variable may change during execution. If you declare a variable in C, that means you are asking the operating system to reserve a piece of memory with that variable name.

Variable Declaration in C


type variable_name;


type variable_name, variable_name, variable_name;

Variable Declaration and Initialization


int    width, height=5;
char   letter='A';
float  age, area;
double d;

/* actual initialization */
width = 10;
age = 26.5;

Variable Assignment

A variable assignment is the process of assigning a value to a variable.


int width = 60;
int age = 31;

There are some rules on choosing variable names

  • A variable name can consist of Capital letters A-Z, lowercase letters a-z, digits 0-9, and the underscore character.
  • The first character must be a letter or underscore.
  • Blank spaces cannot be used in variable names.
  • Special characters like #, and $ are not allowed.
  • C keywords cannot be used as variable names.
  • Variable names are case-sensitive.
  • Values of the variables can be numeric or alphabetic.
  • Variable type can be char, int, float, double, or void.

C Program to Print Value of a Variable



void main()
    int age = 33; // c program to print value of a variable
    printf("I am %d years old.\n", age);

Program Output:

I am 33 years old.

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