SAMPLE: High-Resolution Timing Services

• Microsoft Software Development Kit (SDK) for Windows version 3.0

SUMMARY

TIMESMP is a file in the Microsoft Software Library that demonstrates using the high-resolution timer services provided by the Microsoft Multimedia Windows graphical environment.

Download TIMESMP.EXE from the Microsoft Software Library (MSL) on the following services:

• Microsoft Download Service (MSDL)

        Dial (206) 936-6735 to connect to MSDL
        Download TIMESMP.EXE (size: 20818 bytes) 
  

• Internet (anonymous FTP)

        ftp ftp.microsoft.com
        Change to the \SOFTLIB\MSLFILES directory
        Get TIMESMP.EXE (size: 20818 bytes) 
  

MORE INFORMATION

The timer services provided by Multimedia Windows allow an application to schedule timed periodic interrupts or one-time interrupt events at a higher resolution than is available through the standard Windows timer services.

Unlike the Windows timer services, the Multimedia timer services are interrupt-based. Rather than posting WM_TIMER messages to a message queue, the Multimedia service calls a specified function at interrupt time. Because the callback code is accessed at interrupt time, it must adhere to strict programming guidelines. In particular, only a very limited set of system function calls may be made, and the callback function must reside in a fixed-code dynamic-link library (DLL).

The Multimedia timer services are useful for applications that demand high-resolution timing, such as a MIDI sequencer. For less demanding synchronization tasks, use the SetTimer function provided by Windows.

The sample application TIMESMP demonstrates using the timer services and a callback function residing in a fixed code DLL.