CC++言語のタイミング関数

1.中関数clock()は、タイプclock_を返します.t,精度,ミリ秒レベル

#include  
#include  
#include  

void test() 
{ 
	int i = 0; 
	int j = 0; 
	double a = 0; 

	while (i++ < 1000000) 
		while (j++ < 1000000) 
		{ 
			a = sqrt(2.0); 
		} 
} 

int main(void) 
{ 
	clock_t start, finish; 
	double  duration = 0.0; 

	start = clock(); 

	test(); 

	finish = clock(); 
	duration = (double)(finish - start); //    ms
	duration = (double)(finish - start) / CLOCKS_PER_SEC; //     s, //#define CLOCKS_PER_SEC 1000 
	
	printf("%f seconds
", duration);  

	return 0; 
} 

2.       ：QueryPerformanceCounter          ，         ，          ，           ，        ，              。

#include  
#include  
#include  
#include 

void test() 
{ 
	int i = 0; 
	int j = 0; 
	double a = 0; 

	while (i++ < 1000000) 
		while (j++ < 1000000) 
		{ 
			a = sqrt(2.0); 
		} 
} 

int main(void) 
{ 
	LARGE_INTEGER start; 
	LARGE_INTEGER end; 
	LARGE_INTEGER freq; 

	QueryPerformanceFrequency(&freq); 
	QueryPerformanceCounter(&start); 

	test();  

	QueryPerformanceCounter(&end); 

	printf("user time : %.10f seconds
", (double)(end.QuadPart - start.QuadPart) / (double)freq.QuadPart); 

	return 0; 
} 

3.    time(&t)，    ，    

  ：       ， 1970 1 1       00:00:00       ，          t ，             。 

#include  
#include  
#include  
#include  
#include 
int main() 
{ 
	time_t t; 
	time(&t); 
	printf("Today's date and time: %s",ctime(&t)); 

	time_t first, second; 
	first=time(NULL); 
	Sleep(2000); 
	second=time(NULL); 
	printf("The difference is: %f seconds",difftime(second,first)); 
	getch(); 

	return 0; 
}