Path: utzoo!attcan!lsuc!ncrcan!brian
From: brian@ncrcan.Toronto.NCR.COM (Brian Onn)
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re: Splitting up KA9Q-net (was: Re: Anomalies with KA9Q)
Message-ID: <1010@ncrcan.Toronto.NCR.COM>
Date: 14 Nov 88 03:23:24 GMT
References: <8811091318.aa29770@Louie.UDEL.EDU> <8811102102.AA00584@b-tech.ann-arbor.mi.us>
Reply-To: brian@ncrcan.Toronto.NCR.COM (Brian Onn)
Organization: NCR Canada Ltd., Mississauga, Ontario
Lines: 31

In article <8811102102.AA00584@b-tech.ann-arbor.mi.us> zeeff@b-tech.ann-arbor.mi.us (Jon Zeeff) writes:
>It seems entirely feasible to run multiple threads within a single dos program
>- all you need is a small interrupt driven kernel to do scheduling and 
>i/o.  I've heard that some of the Microsoft C library routines are not
>reentrant though.   Has anyone implemented a kernel for something like this?

Yes, I have.  It was a satellite interface on an MSDOS machine.  The software
had to monitor outgoing satellite data, and capture and process incoming 
satellite data.  Logging to the printer, and data re-transmission (ie
RS232 repeater) was also implemented.  The thing was basically as you
described, a multi-threaded DOS program.  The scheduler was driven from
a table with a maximum of 10 threads allowed.  Each thread got a slice of
the CPU, taken away via the timer interrupt.  There was rudimentary message
passing between the threads, and also a limited memory pool (to allocate 
the message buffers from).  The whole thing ran in the "background", to
allow an operator to use a word processor at the same time. The files 
created with the word processor would ultimately be sent up to the
satellite.

Non re-entrant C libraries?  I suppose that any library routines that
keep a static variable storage would not be re-entrant.  

DOS and BIOS re-entrancy is another story.

Brian.

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