Prime or not prime, using loop::

#include<conio.h>

#include<stdio.h>

void main()

{clrscr();

int i,n,a,b;

printf("enter a number=");

scanf("%d",&n);

a=0;

for(i=2;i<=n;i++)

{b=n%2;

if(b==0)

{a=1;}

       }

if(a==1)

{printf("not prime");}

else

{printf("prime number");}

getch();}