Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: notesfiles - hp 1.2 08/01/83; site hp-pcd.UUCP
Path: utzoo!linus!decvax!tektronix!hplabs!hp-pcd!bill
From: bill@hp-pcd.UUCP (bill)
Newsgroups: net.micro.pc
Subject: MS-DOS function 37h
Message-ID: <15200001@hpcvlo.UUCP>
Date: Tue, 9-Jul-85 13:44:00 EDT
Article-I.D.: hpcvlo.15200001
Posted: Tue Jul  9 13:44:00 1985
Date-Received: Mon, 15-Jul-85 01:43:47 EDT
Organization: Hewlett-Packard - Corvallis, OR
Lines: 29
Nf-ID: #N:hpcvlo:15200001:000:788
Nf-From: hpcvlo!bill    Jul  9 09:44:00 1985


Somebody a while back asked about MS-DOS function 37h, mentioning that
it responded to AL values of 0, 1, 2, and 3 ... but couldn't figure
out what the last two functions were supposed to do.

I don't know about later versions, but in MS-DOS 2.11 the functions are:

	Specify:

	AH=37h
	AL=0	Read switch character (returns current character in DL)
	   1	Set switch character (specify new character in DL)
	   2	Read device availability (as set by function AL=3)
	   3	Set device availability, where:
		DL=0 means /DEV/ must preceed device names
		DL#0 means /DEV/ need not preceed device names

	Returns:

	DL =	Switch character (if AL=0 or 1)
		Device availability flag (if AL=2 or 3)

	Error return:	

	AL=0FFh means the value in AL was not in the range 0-3.


Bill Frolik
hp-pcd!bill