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From: cd5340@mars.njit.edu (Charlap)
Newsgroups: comp.os.msdos.programmer
Subject: Re: TSR PROGRAMMING PROBLEM
Message-ID: <2168@njitgw.njit.edu>
Date: 29 Jan 91 23:10:04 GMT
References: <8256@ucdavis.ucdavis.edu> <1991Jan29.173752.10045@bronze.ucs.indiana.edu> <5369@trantor.harris-atd.com>
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In article <5369@trantor.harris-atd.com> sonny@trantor.harris-atd.com (Bob Davis) writes:
>In article <1991Jan29.173752.10045@bronze.ucs.indiana.edu> yawei@bronze.ucs.indiana.edu (mr. yawei) writes:
>>In article <8256@ucdavis.ucdavis.edu> chiang@iris.ucdavis.edu (Tom Chiang) writes:
>>>
>	[DELETIONS]
>>
>>This is called the DOS re-entrancy problem which anyone who is teaching
>>you to write TSRs should have told you about. Simply speaking, DOS
>>cannot be entered twice.

Not quite.  DOS re-enters itself all over the place.  There is a scheduler
interrupt (I forget what it is, though) which is very undocumented, which
many hackers use for making re-entrant TSR's.  Most notable of these is the
DOS PRINT command, which uses the scheduler interrupt in order to do background
printing.

Does anyone have more info?  Something was mentioned in the book "The MS-DOS
BIBLE" by the Waite group, but it isn't too detailed.

--- Dave (cd5340@mars.njit.edu)