A simpler timer class and its demo, using QueryPerformanceCounter. (therefore works only on windows platform)

SimpleTimer.cpp

#include "SimpleTimer.h"

/**
  Initialize, call application start time before updating frame.
*/
void SimpleTimer::start()
{
  // from MSDN:  On systems that run Windows XP or later, 
  // the function will always succeed and will thus never return zero.
  (void)QueryPerformanceFrequency(&freq);
  (void)QueryPerformanceCounter(&start_time);

  last_time = start_time;
}

/**
  Return elapsed time as miliseconds.
*/
float SimpleTimer::tick()
{
  float dt;
  LARGE_INTEGER current_time;
  QueryPerformanceCounter(&current_time);

  if (last_time.QuadPart == start_time.QuadPart)
    dt = 1.0f / 60.0f;
  else
    dt = static_cast<float>(static_cast<double>(current_time.QuadPart - last_time.QuadPart) / static_cast<double>(freq.QuadPart));

  last_time = current_time;

  return dt;
}

/**
  Return elapsed time as miliseconds.
*/
float SimpleTimer::total()
{
  float dt;
  LARGE_INTEGER current_time;
  QueryPerformanceCounter(&current_time);

  if (last_time.QuadPart == start_time.QuadPart)
    dt = 1.0f / 60.0f;
  else
    dt = static_cast<float>(static_cast<double>(current_time.QuadPart - start_time.QuadPart) / static_cast<double>(freq.QuadPart));

  last_time = current_time;

  return dt;
}

SimpleTimer.h

#pragma once
#include <windows.h>

/**
  A simple timer(only for windows platform)
*/
class SimpleTimer
{
public:
  void start();
  float tick();
  float total();

private:
  LARGE_INTEGER freq;
  LARGE_INTEGER start_time;
  LARGE_INTEGER last_time;
};

test.cpp

#include <iostream>
#include "SimpleTimer.h"

int main()
{
  SimpleTimer timer;
  timer.start();

  while (1)
  {
    // put elapsed time at every 20ms.
    // it will put approx. 0.020xxx.
    float elapsed = timer.tick();
    printf("elapsed: %f\n", elapsed);
    
    // break after passing 2sec.
    float total = timer.total();
    if (total > 2.0)
      break;
    
    // sleep 20ms.
    Sleep(20);
  }

  return 0;
}