Category: <b>DOS kernel</b>
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<pre><b>INT 21 - DOS 5+ - GET OR SET UMB LINK STATE</b>

	AH = 58h
	AL = subfunction
	    02h get UMB link state
		Return: AL = current link state
			    00h UMBs not part of DOS memory chain
			    01h UMBs in DOS memory chain
	    03h set UMB link state
		BX = new link state
		    0000h remove UMBs from DOS memory chain
		    0001h add UMBs to DOS memory chain
Return: CF clear if successful
	CF set on error
	    AX = error code (01h) (see <a href=../../it/80/16.html>#01680</a>)
Notes:	a program which changes the UMB link state should restore it before
	  terminating
	UMBs will only be available if CONFIG.SYS contains the line DOS=UMB,
	  the UMBs have been linked into the memory chain with AX=5803h, and
	  the allocation strategy has been set to include high memory with
	  AX=5801h
SeeAlso: <a href=../../it/87/16.html>#01687</a>,<a href=../../it/66/27.html>#02766</a> at INT 2F/AX=4310h
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