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From: "Kumar, Rao                  CO" <KUMAR@BOGPO1.CO.unisys.com>
To: "questions@freebsd.org" <questions@freebsd.org>
Subject: Help!
Date: Fri, 23 Aug 96 16:10:00 GMT
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Hello

Thanks in advance for your time. I saw your mail id on the Internet. So I am 
sending you this mail
and would highly appreciate your help.

I have written a TSR (that runs on MS DOS 6.2) that intercepts the interrupt 
 1C (timer interrupt). What I am
 trying to do in this interrupt handler is some file i/o (using fopen, fread 
and fclose of Microsoft C).
At times the system hangs. I thought it was due to some conflict in 
simultaneous handling of interrupt 21h by the file i/o calls inside my 
routine and the foreground application. So I tried to do a check for the 
InDOS
flag before proceeding with my interrupt handling routine, but this flag is 
always 1 when my interrupt
routine is invoked (even when there is no front end application).
My questions are :
1. Why the InDOS flag is always 1 when my interrupt routine is invoked ? 
 (my routine handles the
interrupt 1C)
2. Is there any other way to know if MS DOS is executing a 21h interrput ?
Thanks again.

Kumar