Chapter 5. Windows Interrupt 2Fh Interface
The Microsoft® Windows® Interrupt 2Fh services and notifications help Windows device drivers and related MS-DOS device drivers and terminate-and-stay-resident (TSR) programs manage their operations in the multitasking environment of Windows. The services let drivers carry out actions such as relinquishing the CPU time slice. The notifications let drivers respond to events, such as starting up Windows, that Windows broadcasts using Interrupt 2Fh.
Services and Notifications
The Interrupt 2Fh services are a set of functions that MS-DOS drivers and TSRs call to direct Windows to carry out specific actions. The notifications are a set of functions that Windows calls to notify drivers and programs of Windows-related events. Although these functions were initially designed for use by MS-DOS drivers and TSRs, some Windows device drivers, such as display drivers and grabbers, also use them to manage the multitasking features of Windows.
A driver can call the service functions using the MS-DOS multiplex interrupt, Interrupt 2Fh. The driver sets one or more registers to specified values, sets the AX register to the desired function number, and issues the interrupt using the int instruction.
A driver can receive notifications by installing its own interrupt-handling routine in the Interrupt 2Fh interrupt chain. Once the interrupt handler is installed, the driver checks the AX register on each interrupt for function numbers that match the notifications. When the driver matches a notification, it can carry out any related actions.
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