什么是值为真？使用整数作为while循环控制器条件

#include <stdio.h>
int main(void)
{
    int n = 3;

    while (n)
        printf("%2d is true/n", n--);
    printf("%2d is false/n", n);

    n = -3;
    while (n)
        printf("%2d is true/n", n++);
    printf("%2d is false/n", n);

    return 0;
}