Path: utzoo!attcan!uunet!mcvax!ukc!reading!cf-cm!cybaswan!iiit-sh
From: iiit-sh@cybaswan.UUCP (Steve Hosgood)
Newsgroups: comp.sys.ibm.pc
Subject: Help from TSR Gurus requested
Keywords: TSR, PSP, Process, Allocation
Message-ID: <536@cybaswan.UUCP>
Date: 5 Jul 89 12:15:31 GMT
Organization: Institute for Industrial Information Technology
Lines: 34

The Program Segment Prefix (PSP) of a normal DOS command is the 100h bytes
before the start of the code proper, and contains:

00-5B:	Reserved stuff
5C-6B:	Default FCB #1
6C-7B:	Default FCB #2
80-FF:	Command Tail and default DTA.
100:	Start of program area

The rules for normal processes state "do *not* alter the area below 5Ch". I
am given to understand that the area below 5Ch is used by DOS to keep track of
processes in memory, and to remove them when they complete.

Now the Question: Can the resident part of a TSR get away with using the area
below 5Ch? I would *think* that DOS has no further use for the PSP after the
program becomes resident, but of course the area may still figure
in some sort of linked-list internally in DOS.

Any info please? I'll summarise any email I get to the net.
Steve

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Steve Hosgood BSc,                             | Phone (+44) 792 295213
Image Processing and Systems Engineer,         | Fax (+44) 792 295532
Institute for Industrial Information Techology,| Telex 48149
Innovation Centre, University of Wales, +------+ JANET: iiit-sh@uk.ac.swan.pyr
Swansea SA2 8PP                         | UUCP: ..!ukc!cybaswan.UUCP!iiit-sh
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            My views are not necessarily those of my employers!
-- 
-----------------------------------------------+------------------------------
Steve Hosgood BSc,                             | Phone (+44) 792 295213
Image Processing and Systems Engineer,         | Fax (+44) 792 295532
Institute for Industrial Information Techology,| Telex 48149