Category: <b>DOS extenders</b>
<br>Flags: available only in protected mode<p>
<pre><b>INT 31 - DPMI 0.9+ - ALLOCATE REAL MODE CALLBACK ADDRESS</b>

	AX = 0303h
	DS:(E)SI = selector:offset of procedure to call
	ES:(E)DI = selector:offset of real mode call structure (see <a href=../../it/48/31.html>#03148</a>)
Return: CF clear if successful
	    CX:DX = segment:offset of real mode call address (see <a href=../../it/49/31.html>#03149</a>)
	CF set on error
	    AX = error code (DPMI 1.0+) (8015h) (see <a href=../../it/43/31.html>#03143</a>)
Notes:	the real mode call structure is static, causing reentrancy problems;
	  its contents are only valid at the time of a callback
	the called procedure must modify the real mode CS:IP before returning
	values are returned to real mode by modifying the real mode call struc
	DPMI hosts must provide at least 16 callbacks per client
	the limited DPMI host built into Phar Lap's 286|DOS-Extender v2.5 does
	  not support this function
BUG:	Windows NT 4.0 either ignores or clears the high 16 bits of EDI,
	  causing an illegal instruction error if the real mode call
	  structure's offset in ES is greater than 64K
SeeAlso: AX=0304h,AX=0C00h

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