/* Prime number - Program  to check whether a given number is prime or not */

/* Assume 2 is a prime number but 0 and 1 are not */

#include  <stdio.h>
#include  <conio.h>

void main()
{
    int  p,d, flag ;
    clrscr() ;
    printf("Enter a number: ") ;
    scanf("%d", &p) ;
    flag=1 ;     /* Assuming p is prime */
    for(d=2 ; d<=p-1 ; d++)   /* d<=p/2 is also correct */
        if(p%d==0)     /* True if number is not prime */
            {
                flag=0 ;
                break ;    /* Loop terminates if p is not prime  */
            }
    if(flag==0 || p==1 || p==0 )
        printf("%d is not prime", p) ;
    else
        printf("%d is prime", p) ;
    getch() ;
}

/*
Output 1:

Enter a number: 1
1 is not prime

Output 2:

Enter a number: 7
7 is prime

Output 3:

Enter a number: 9
9 is not prime
*/