Check prime or Not in C programming

Write a C program to check whether a given number is 

prime or not 

What is Prime number ?

    A prime number is a positive integer that is divisible only by 1 and itself.

For Example , 5 ,7,11,17...etc

Program for prime or Not

#include<stdio.h>

#include<conio.h>

void main()

{

    int num,i,flag=0;

    printf("\n\t To Check Prime or Not ");

    printf("\n\t ** ***** ***** ** ***");

    printf("\n Input");

    printf("\n Enter a Positive integer : ");

    scanf("%d",&num);

    if(num==0||num==1)

        flag=1;

    for(i=2;i<=num/2;i++)

    {

        if(num%i==0)

        {

            flag=1;

            break;

        }

 }

if (flag==0)

    printf("\n %d is a Prime Number ",num);

else

    printf("\n %d is not a Prime Number ",num);

getch();

}

Output