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=02H
Get Processor Exception Handler Vector
AX = 0202H BL = exception number (00H-1FH)
if function successful Carry flag = clear CX:(E)DX = selector:offset of exception handler if function unsuccessful Carry flag = set AX = error code 8021H invalid value (BL not in range 0-1FH)
Returns the address of the current client's protected mode exception handler for the specified exception number. This function should be avoided by DPMI 1.0 clients.
The value returned in CX is a valid protected mode selector, not a real mode segment address.
32-bit clients will be returned a 32-bit offset in the EDX register.
Clients which run under DPMI 1.0 should use Int 31H Functions 0210H and 0211H to obtain the addresses of exception handlers. This function is supported by DPMI 1.0 hosts solely for compatibility with DPMI 0.9.
Text based on http://www.delorie.com/djgpp/doc/dpmi/