A virtual device can provide Interrupt 2Fh functions by installing a callback procedure for this interrupt. Interrupt 2Fh functions allow applications and other software running in a virtual machine access to the virtual device without requiring the virtual device to provide API procedures. For example, the standard virtual display supports a set of Interrupt 2Fh functions with which it communicates with the Windows display driver.
Windows installs its own Interrupt 2Fh handler and supports a variety of functions to allow MS-DOS device drivers and TSRs to specify actions to take when Windows starts or while a virtual machine runs. For more information about these functions, see the Microsoft Windows Device Driver Adaptation Guide.