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=05H
Set Protected Mode Interrupt Vector
AX = 0205H BL = interrupt number CX:(E)DX = selector:offset of exception handler
if function successful Carry flag = clear if function unsuccessful Carry flag = set AX = error code 8022H invalid selector
Sets the address of protected mode handler for the specified interrupt into the interrupt vector.
The value passed in CX should be a valid protected mode code selector, not a real mode segment address.
32-bit clients must supply a 32-bit offset in the EDX register. If the client's handler chains to the next exception handler it must do so using a 32-bit interrupt stack frame.
DPMI hosts must support all 100H (256 decimal) interrupt vectors with this function.
Hardware interrupts are sent to the primary client of the virtual machine while software interrupts are sent to the current client. (See Appendix A: Glossary for definitions of primary and current client.)
Refer to the rules for descriptor usage in Appendix D.
Text based on http://www.delorie.com/djgpp/doc/dpmi/