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.
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=00H
Get Real Mode Interrupt Vector
AX = 0200H BL = interrupt number
Carry flag = clear (this function always succeeds) CX:DX = segment:offset of real mode interrupt handler
Returns the contents of the current virtual machine's real mode interrupt vector for the specified interrupt.
The value returned in CX is a real mode segment address, not a selector. Attempts to place this value into a segment register in protected mode may cause a general protection (GP) fault.
All 100H (256) real mode interrupt vectors must be made available through this function by the DPMI host.
Text based on http://www.delorie.com/djgpp/doc/dpmi/