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21FF--DH00

Category: DOS extenders
Flags: Undocumented function, available only in protected mode

INT 21 - Rational Systems DOS/4GW - GET VERSION???

	AH = FFh
	DH = 00h
	DL = ??? (78h seen)
Return: CF clear
	EAX = 4734FFFFh (high word is byte-swapped "4G") if DOS/4G installed
Note:	Quarterdeck's DESQview/X X Toolkit library uses this call to determine
	  whether the direct-mapped linear 4GB segment's selector is 34h or 38h
SeeAlso: INT 21/AH=FFh/DH=00h"DOS/4GW"

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