This DPMI 0.9 Specification is hosted by Tenberry Software, Inc.

8. Descriptor Management Services, Continued

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8.3 Segment to Descriptor

This function is used to convert real mode segments into descriptors that are addressable by protected mode programs.

To Call

     AX = 0002h
     BX = Real mode segment address


     If function was successful:
     Carry flag is clear.
     AX = Selector mapped to real mode segment

     If function was not successful:
     Carry flag is set.

Programmer's Notes

Code Sample:

The following function compiles with Watcom C/C++ version 11.0 or later, and Microsoft Visual C/C++ version 4.0 or later:

// allocate one descriptor

int dpmiSegmentToDescriptor(unsigned short realSegment,	// real-mode segment address
			dpmiSelector *pSel)	// (returned) the resulting selector
	int result;			// zero if int 31h succeeds
	unsigned short errorCode;	// error code from DPMI host

	__asm {
		mov	bx, realSegment	// the real-mode segment to map

		mov	eax, 0x002	// call dpmi host to do mapping
		int	0x31

		mov	errorCode, ax	// save error code from DPMI, if any

		sbb	eax, eax	// record success/failure flag
		mov	result, eax

	// if the dpmi call failed, return the dpmi error code
	if (result != 0)
		return errorCode;

	// if we succeeded, AX contained the selector
	*pSel = (dpmiSelector) errorCode;

	// indicate success
	return 0;

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This HTML edition of the DPMI 0.9 Specification is hosted by Tenberry Software, Inc., makers of the DOS/16M and the DOS/4G family of DOS extenders. Page last modified 2003.1.28, <>