An entity that may very during the program execution is known as variable .Variable are the name given location in a memory .rules are

1.  Length is must be 1-31 character

2.  Only alphabet digit & underscore is used.

3.  First character must be an alphabet or an underscore

4.  Name can’t start with digit

5.  Keywords can’t be used

6.  Space & symbol are not allowed

7.  Upper case and lower case are different

 

Example of Variable

 #include<stdio.h>

#include<conio.h>

void main(){

            int i;

            clrscr();

            printf("Enter a value of i:");

            scanf("%d",&i);

            printf("%d",i);

getch();

}  

Output

    Enter value of I = 56

    56