C语言计算机器运行时间

//计算机器运行时间

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");