Timer Event Operations

[The feature associated with this page, Multimedia Timers, is a legacy feature. It has been superseded by Multimedia Class Scheduler Service. Multimedia Class Scheduler Service has been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Multimedia Class Scheduler Service instead of Multimedia Timers, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

After you have established your application's timer resolution, you can start timer events by using the timeSetEvent function. This function returns a timer identifier that can be used to stop or identify timer events. One of the function's parameters is the address of a TimeProc callback function that is called when the timer event takes place.

There are two types of timer events: single and periodic. A single timer event occurs once, after a specified number of milliseconds. A periodic timer event occurs every time a specified number of milliseconds elapses. The interval between periodic events is called an event delay. Periodic timer events with an event delay of 10 milliseconds or less consume a significant portion of CPU resources.

The relationship between the resolution of a timer event and the length of the event delay is important in timer events. For example, if you specify a resolution of 5 and an event delay of 100, the timer services notify the callback function after an interval ranging from 95 to 105 milliseconds.

You can cancel an active timer event at any time by using the timeKillEvent function. Be sure to cancel any outstanding timers before freeing the memory containing the callback function.