c语言计算时间方法---clock-GetTickCount-QueryPerformanceCounter

#include "stdafx.h"
#include <time.h>
#include <stdlib.h>
#include <math.h>

int main(void)
{
	int i,sum=0;
	clock_t start,finish;
	
	start=clock();
	for(i=1;i<10000000;i++)
	{
		sum+=sqrt((float)i);
	}
	finish=clock();

	printf("The time is %dms.\n",finish-start);
	printf("The time is %ds\n",(finish-start)/1000);
	system("pause");
	return 0;
}

#include <stdio.h>
#include <windows.h>

int main(void)
{
	double t0,t1;
	int i;

	t0=GetTickCount();
	Sleep(200);
	t1=GetTickCount();

	printf("----%fms",t1-t0);
	
	getchar();
	return 0;
}

#include <stdio.h>
#include <windows.h>

int main(void)
{
	LARGE_INTEGER freq, freqcnt;
	double dcnt, cnt1, cnt2;

	QueryPerformanceFrequency(&freq);
	dcnt=freq.QuadPart;

	QueryPerformanceCounter(&freqcnt);
	cnt1=freqcnt.QuadPart;
	Sleep(1000);
	QueryPerformanceCounter(&freqcnt);
	cnt2=freqcnt.QuadPart;

	printf("----%fms",(cnt1-cnt2)/dcnt*1000);
	
	getchar();
	return 0;
}