例4--4

#include<stdio.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; }