Note: This API calls are shared between DOS and Win16 personality.
DPMI is a shared interface for DOS applications to access Intel 80286+ CPUs services. DOS DMPI host provides core services for protected mode applications. Multitasking OS with DOS support also provides DMPI in most cases. Windows standard and extended mode kernel is a DPMI client app. Standard and extended mode kernel differs minimally and shares common codebase. Standard Windows kernel works under DOSX extender. DOSX is a specialized version of 16-bit DPMI Extender (but it is standard DPMI host). Standard mode is just DPMI client, exnhanced mode is DPMI client running under Virtual Machime Manager (really, multitasker which allow to run many DOS sessions). Both modes shares DPMI interface for kernel communication. The OS/2 virtual DOS Protected Mode Interface (VDPMI) device driver provides Version 0.9 DPMI support for virtual DOS machines. Win16 (up to Windows ME) provides Version 0.9 DPMI support. Windows in Standard Mode provides DPMI services only for Windows Applications, not DOS sessions.
DPMI host often merged with DPMI extender. Usually DPMI extender provide DPMI host standard services and DOS translation or True DPMI services.
Int 31H, AH=02H, AL=01H
Version
0.9
Brief
Set Real Mode Interrupt Vector
Input
AX = 0201H
BL = interrupt number
CX:DX = segment:offset of real mode interrupt handler
Return
Carry flag = clear (this function always succeeds)
Notes
The address passed in CX must be a real mode segment address, not a selector. Consequently, the interrupt handler must either reside in DOS memory (i.e. below the 1 MB boundary) or the client must allocate a real mode callback address. See Int 31H Functions 0100H and 0303H.
If the interrupt being hooked is a hardware interrupt, the memory that the interrupt handler uses must be locked.
See also
Note
Text based on http://www.delorie.com/djgpp/doc/dpmi/