#include<stdio.h>

int prime(int); 

int main(void)

{

int num,i; 

printf(“input a positive number:”);

scanf(“%d”,&num); 

printf(“all the primes<=%d:\n”,num);

for(i=2;i<=num;i++)

if(prime(i))

printf(“%d\t”,i);

printf(“\n”);

return 0;

} 

int prime(int n)

{

int div; 

for(div=2;div*div<=n;div++)

if(n%div==0)

return 0;

return 1;

}