C计算程序运行时间

#include “stdio.h”
#include “stdlib.h”
#include “time.h”

int main( void )
{
    long     i = 10000000L;
    clock_t start, finish;
    double   duration;
    /* 测量一个事件持续的时间*/
    printf( "Time to do %ld empty loops is ", i );
    start = clock();
    while( i-- )       ;
    finish = clock();
    duration = (double)(finish - start) / CLOCKS_PER_SEC;
    printf( "%f seconds/n", duration );
    system("pause");
}

在笔者的机器上，运行结果如下：

Time to do 10000000 empty loops is 0.03000 seconds

在标准C/C++中，最小的计时单位是一毫秒