Category: <b>DESQview/TopView and Quarterdeck programs</b>
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<pre><b>INT 21 - DESQview - INSTALLATION CHECK</b>

	AH = 2Bh
	CX = 4445h ('DE')
	DX = 5351h ('SQ')
	AL = subfunction (DV v2.00+)
	    01h get version
		Return: BX = version (BH = major, BL = minor)
		Note: early copies of v2.00 return 0002h
	    02h get shadow buffer info, and start shadowing
		Return: BH = rows in shadow buffer
			BL = columns in shadow buffer
			DX = segment of shadow buffer
	    04h get shadow buffer info
		Return: BH = rows in shadow buffer
			BL = columns in shadow buffer
			DX = segment of shadow buffer
	    05h stop shadowing
Return: AL = FFh if DESQview not installed
Notes:	in DESQview v1.x, there were no subfunctions; this call only identified
	  whether or not DESQview was loaded.  DESQview v2.52 performs function
	  01h for all subfunction requests 0Ch and higher and appears to ignore
	  all lower-numbered functions not listed here.
	DESQview versions 2.50-2.52 are part of DESQview/X v1.0x; version 2.53
	  is part of DESQview/X v1.10; and version 2.63 is part of DESQview/X
	  v2.00.
BUG:	subfunction 05h does not appear to work correctly in DESQview 2.52
SeeAlso: INT 10/AH=FEh,INT 10/AH=FFh,INT 15/AX=1024h,INT 15/AX=DE30h
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