Compatibility: 5.0+

Expects: AX    4B01H  (INT 2fH)

CX:DX address of switcher service function handler

ES:BX 0000:0000 (on initial call; see below)

...or...

address of a SwCallbackInfoRec needing processing (when

intercepting this INT 2fH fn; see below)

Returns: ES:BX 0000:0000 (on initial call)

...or...

address of a local SwCallBackInfoRec (when intercepting)

Info: This fn creates a linked list of notification function handlers.

Applications which need to be notified of task-switcher

activities may intercept this fn and process subsequent calls

(made by other programs) as follows:

If you don't need to process switcher notifications, just JMP to

the previous INT 2fH handler.

If you do need notifications, your INT 2fH handler should:

  First, chain to any previously-installed handlers by pushing

the FLAGS register and performing a FAR CALL to the previous

handler.

  On return from that CALL, create a SwCallbackInfoRec from local

memory and fill it in (including the address of your code that

will handle switcher notifications).   Copy the returned value

of ES:BX into the pfNextHandler field of the structure.

  Place the address of your own SwCallbackInfoRec into ES:BX and

execute an IRET.

These steps result in a chain of INT 2fH handlers, each of which

can process subsequently-installed handlers.

See Also: INT 2fH 4BxxH: Task Switcher Functions

Switcher Services and Notifications

INT 2fH: Multiplex Interrupt

DOS Functions

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