Windows broadcasts the notification functions by setting registers and issuing Interrupt 2Fh. Drivers and TSRs use the notifications to load Windows installable devices, free extended memory, and enable or disable various device services or features. There are the following notification functions:
Windows Initialization Notification (Interrupt 2Fh Function 1605)
Windows Termination Notification (Interrupt 2Fh Function 1606h)
Device Call Out (Interrupt 2Fh Function 1607h)
Windows Initialization Complete Notification (Interrupt 2Fh Function 1608h)
Windows Begin Exit (Interrupt 2Fh Function 1609h)
MS-DOS device drivers, such as network drivers, use Windows Initialization Notification to direct Windows to load a protected-mode installable device that provides 32-bit support for the real-mode driver while Windows runs. Other MS-DOS drivers (for example, disk-cache drivers) use the same notification to free any extended memory before Windows starts. The TSRs also use Windows Termination Notification to reclaim the extended memory when Windows stops.
If an MS-DOS driver or TSR programs installs a corresponding virtual device, that device can send notifications of its own to the driver or TSR using Device Call Out.
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