Variables are memory locations(storage area) 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, variables value 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 a 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 #, $ 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.