The reason for using concurrency technology is to master event driven programming more easily
event-driven programming
In event driven programming
Where these events occur is unpredictable

Coupling if it's a problem
Can be avoided in command mode
Through command mode
"Normal" operations do not need to know any information about the time they checked
They are separated from the event handling code

//: C10:MulticastCommand.cpp {RunByHand}
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Decoupling event management with the Command pattern.
#include <iostream>
#include <vector>
#include <string>
#include <ctime>
#include <cstdlib>
using namespace std;

// Framework for running tasks:
class Task {
public:
  virtual void operation() = 0;
};

class TaskRunner {
  static vector<Task*> tasks;
  TaskRunner() {} // Make it a Singleton
  TaskRunner& operator=(TaskRunner&); // Disallowed
  TaskRunner(const TaskRunner&); // Disallowed
  static TaskRunner tr;
public:
  static void add(Task& t) { tasks.push_back(&t); }
  static void run() {
    vector<Task*>::iterator it = tasks.begin();
    while(it != tasks.end())
      (*it++)->operation();
  }
};

TaskRunner TaskRunner::tr;
vector<Task*> TaskRunner::tasks;

class EventSimulator {
  clock_t creation;
  clock_t delay;
public:
  EventSimulator() : creation(clock()) {
    delay = CLOCKS_PER_SEC/4 * (rand() % 20 + 1);
    cout << "delay = " << delay << endl;
  }
  bool fired() {
    return clock() > creation + delay;
  }
};

// Something that can produce asynchronous events:
class Button {
  bool pressed;
  string id;
  EventSimulator e; // For demonstration
public:
  Button(string name) : pressed(false), id(name) {}
  void press() { pressed = true; }
  bool isPressed() {
    if(e.fired()) press(); // Simulate the event
    return pressed;
  }
  friend ostream&
  operator<<(ostream& os, const Button& b) {
    return os << b.id;
  }
};

// The Command object
class CheckButton : public Task {
  Button& button;
  bool handled;
public:
  CheckButton(Button & b) : button(b), handled(false) {}
  void operation() {
    if(button.isPressed() && !handled) {
      cout << button << " pressed" << endl;
      handled = true;
    }
  }
};

// The procedures that perform the main processing. These
// need to be occasionally "interrupted" in order to
// check the state of the buttons or other events:
void procedure1() {
  // Perform procedure1 operations here.
  // ...
  TaskRunner::run(); // Check all events
}

void procedure2() {
  // Perform procedure2 operations here.
  // ...
  TaskRunner::run(); // Check all events
}

void procedure3() {
  // Perform procedure3 operations here.
  // ...
  TaskRunner::run(); // Check all events
}

int main() {
  srand(time(0)); // Randomize
  Button b1("Button 1"), b2("Button 2"), b3("Button 3");
  CheckButton cb1(b1), cb2(b2), cb3(b3);
  TaskRunner::add(cb1);
  TaskRunner::add(cb2);
  TaskRunner::add(cb3);
  cout << "Control-C to exit" << endl;
  while(true) {
    procedure1();
    procedure2();
    procedure3();
  }
  getchar();
} ///:~

output
delay = 750
delay = 1250
delay = 4750
Control-C to exit
Button 1 pressed
Button 2 pressed

The command object is represented by a Task pointed to by a single TaskRunner
Event simulator creates a random delay time
When the function fire() is called periodically
In a random time period
The return result of the filter changes from true to false