## MMPM/2 Device Driver Reference

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### IOCtl Functions

OS/2 device drivers are used to access the I/O hardware. The IOCtl functions provide a method for an application, or subsystem, to send device -specific control commands to a physical device driver. These IOCtls are subfunctions that are issued through the DosDevIOCtl function request. The DosDevIOCtl request can be used only by OS/2 applications; the INT 21h IOCtl request can be used only by DOS applications.

This reference describes audio (category 80h) and video (category 140h) IOCtls.