C Variables

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

Syntax:

type variable_name;

or

type variable_name, variable_name, variable_name;

Variable Declaration and Initialization

Example:

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.

Example:

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

Example:

#include<stdio.h>

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.