第四章例4-4

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

 printf("Enter a number:");
 scanf("%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;
}