PEL-Protocol Engineering Lab.

/* prime.c: prints out all the prime numbers less than 100 */
#include <stdio.h>
 
#define N 1000
 
void main(void) {
    int i, j, a[N + 1]; 
 
    for(a[1] = 0, i = 2; i <= N; i++)
        a[i] = 1;
 
    for(i = 2; i <= N/2; i++)
        for(j = 2; j <= N/i; j++)
            a[i * j] = 0;
 
    for(i = 1; i <= N; i++)
        if(a[i])
            printf("%4d", i); 
 
    printf("\n");
}