如果一个系统包含高精度性能计数器（HRPC，high-resolution performance counter）则此系统提供高精度定时器。你可以使用API函数QueryPerformanceFrequency来获得HRPC的频率HRPCF，返回值为cps（counts per second）。这个依赖于处理器（processor dependent），在一些处理器中HRPCF的值可能就是处理器时钟周期（the cycle rate of the processor clock），比如我们测试，在3.0GHZ的Pentium4处理器（Windows2000 Professional）上得到HSPCF=3000360000，在一个2.8GHZ的Pentium4处理器（Windows XP）上得到HSPCF=2800360000，而在一个2.4GHZ的Pentium4处理器（Windows2000 Server）上得到HSPCF= 3579545。使用另外一个函数QueryPerformanceCounter来获取（retrieve）HRPC的值，QPF和QPC的函数原型分别为：BOOL QueryPerformanceFrequency(LARGE_INTEGER *lpFrequency);BOOL QueryPerformanceCounter(     LARGE_INTEGER *lpPerformanceCount);    QPC和QPF函数都在winbase.h中定义。函数中用到的数据类型可以参考如下typedef __int64 LONGLONG;typedef unsigned __int64 ULONGLONGtypedef unsigned long DWORD; typedef union union {    struct {           DWORD LowPart;          LONG HighPart;    };    LONGLONG QuadPart;} LARGE_INTEGER, *PLARGE_INTEGER;在一段代码的前后调用两次HPC函数，就能知道这段代码执行消耗了多少CPU周期或时间，这对于不同算法的性能测试很有帮助，下面有一个例子来进行演示。另外利用循环也可以实现定时功能。那么怎么根据得到的两个HRPC计算时间呢？因为知道了HRPCF是表示HRPC的频率，所以就可以知道HRPC数值每增加1所代表的时间：HRPC second per count       dHMSecondPerCount = 1.0   / HRPCF ;  //spcHRPC millisecond per count  dHMMillisecondPerCount = 1.0E3 / HRPCF ;  //mspcHRPC microsecond per count  dHMMicrosecondPerCount = 1.0E6 / HRPCF ;  //uspc知道这三个值就可以根据两个HRPC差值（difference），即diff=HRPC2-HRPC1，这样就可以计算出两次调用QPC函数经过（elapse）的时间：QueryPerformanceCounter( &HRPC1);//code to be timedQueryPerformanceCounter( &HRPC2);diff=HRPC2-HRPC1;Elapsed second       = diff * dHMSecondPerCount  ;Elapsed millisecond  = diff * dHMMillisecondPerCount ;Elapsed microsecond  = diff * dHMMicrosecondPerCount  ;例程如下：/****************************author:Wandytime: 2005-11-25file: demoForHighResolutionTimer.cppversion:1.0environment:VS.NET2003 + Windows2000Serverabstract:demo for High-Resolution Timer*****************************/＃i nclude <windows.h>＃i nclude <stdio.h> void main() {    LARGE_INTEGER liFrequency;   LARGE_INTEGER liStart;   LARGE_INTEGER liEnd;   LONGLONG liDiff;//or LARGE_INTEGER diff;    double dHMSecondPerCount;//how many second per count   double dHMMillisecondPerCount;//how many millisecond per count   double dHMMicrosecondPerCount;//how many microsecond per count     //set the current Process and Thresd to a high priority   DWORD dwOldProcessP = GetPriorityClass(GetCurrentProcess());   DWORD dwOldThreadP = GetThreadPriority(GetCurrentThread());   SetPriorityClass(GetCurrentProcess(), REALTIME_PRIORITY_CLASS);   SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL);    // Save the performance counter frequency for later use.   if ( !QueryPerformanceFrequency( &liFrequency ) )        printf( "QPF() failed with error %d\n", GetLastError() );   else        printf( "HRPCF: %I64d \n",liFrequency.QuadPart );    //   dHMSecondPerCount      = 1.0    / (double)liFrequency.QuadPart;   dHMMillisecondPerCount = 1.0E3  / (double)liFrequency.QuadPart;   dHMMicrosecondPerCount = 1.0E6  / (double)liFrequency.QuadPart;   printf("dHMSecondPerCount:     %g spc \n", dHMSecondPerCount);   printf("dHMMillisecondPerCount:%g mspc\n", dHMMillisecondPerCount);   printf("dHMMicrosecondPerCount:%g uspc\n", dHMMicrosecondPerCount);       //start   if ( !QueryPerformanceCounter( &liStart ) )      printf( "QPC() failed with error %d\n", GetLastError() );   else        printf( "start HRPC: %I64d \n", liStart.QuadPart );    //code to be timed   Sleep( 100 );    //end   if ( !QueryPerformanceCounter( &liEnd ) )      printf( "QPC() failed with error %d \n", GetLastError() );   else      printf( "end HRPC: %I64d \n", liEnd.QuadPart );    //print diff   liDiff = liEnd.QuadPart - liStart.QuadPart;    printf( "HRPC diff:%I64d and  ms elapsed: %fms\n", liDiff,(double)liDiff * dHMMillisecondPerCount );    //restore the process and thread priority   SetThreadPriority(GetCurrentThread(), dwOldThreadP);   SetPriorityClass(GetCurrentProcess(), dwOldProcessP);      //wait for press any key   getchar();}在我的机器上的执行结果为HRPCF: 3579545dHMSecondPerCount:     2.79365e-007 spcdHMMillisecondPerCount:0.000279365 mspcdHMMicrosecondPerCount:0.279365 uspcstart HRPC: 94756807361end HRPC: 94757165865HRPC diff:358504 and  ms elapsed: 100.153511ms