time.h里的clock()怎么用啊
程序如下:#include <time.h>
#include <stdio.h>
#include <dos.h>
int main(void)
{
clock_t start, end;
start = clock();
delay(20000);
end = clock();
printf("The time was: %f\n", (end - start) / CLK_TCK);
return 0;
}
但我在delay()里的数字无论怎么改,输出要么不变,要么就是0,怎么回事啊,,请帮忙解释下,谢谢