Note: This API calls are shared between DOS and Win16 personality.
DOSX is a specialized version of DPMI. Windows standard and extended mode kernel is a DPMI client app. Standard and extended mode kernel differs minimally and shares common codebase. Standard mode is just DPMI client, exnhanced mode is DPMI client running under Virtual Machime Manager. 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 provides Version 1.0 DPMI support, but reported as 0.9.
Int 31H, AH=01H, AL=01H
Free DOS Memory Block
AX = 0101H DX = selector of block to be freed
if function successful Carry flag = clear if function unsuccessful Carry flag = set AX = error code 0007H memory control blocks damaged (also returned by DPMI 0.9 hosts). 0009H incorrect memory segment specified (also returned by DPMI 0.9 hosts). 8022H invalid selector
Frees a memory block that was previously allocated with the Allocate DOS Memory Block function (Int 31H Function 0100H).
All descriptors allocated for the memory block are automatically freed by this function, and are no longer valid after this function returns.
Under DPMI 1.0 hosts, any segment registers which contain a selector being freed are zeroed by this function.
Refer to the rules for descriptor usage in Appendix D.
Text based on http://www.delorie.com/djgpp/doc/dpmi/