例4-4

#include<stdio.h>
int main(void)
{
    int i,m;

    printf("Enter a number:");
    scanf_s("%d",&m);
    for(i=2;i<=m/2;i++)
        if(m % i==0)
            break;
    if(i>m/2&&m!=1)
        printf("%d is a prime number!\n",m);
    else
         printf("NO!\n");

    return 0;
}