Category: <b>memory management</b>
<br>Flags: callout or callback (usually hooked rather than called), Undocumented function<p>
<pre><b>INT 2F - HIMEM.SYS v2.77+ - GET EXTERNAL A20 HANDLER ADDRESS</b>

	AX = 4330h
Return: AL = 80h if external A20 handler provided
	    ES:BX -&gt; external A20 handler (see <a href=../../it/90/27.html>#02790</a>)
	    CL = A20 detection support
		00h handler is unable to report A20 state
		01h handler supports function 0002h to report A20 state
Note:	HIMEM.SYS calls this function to allow an external program to provide
	  an A20 handler (i.e. to support a machine not supported by HIMEM
	  itself)
SeeAlso: AX=4308h,AX=4310h

</pre>