Category: <b>DOS-based task switchers/multitaskers</b>
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<pre><b>INT 21 - DoubleDOS - INSTALLATION CHECK/PROGRAM STATUS</b>

	AX = F400h
Return: AL = program status
	    00h if DoubleDOS not present
	    01h if running in visible DoubleDOS partition
	    02h if running in the invisible DoubleDOS partition
SeeAlso: AX=E400h,AH=F5h"DoubleDOS"
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