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TSR vs DEVICE= (Announce)

posted by Arjay, 19.06.2010, 19:13

Welcome Bret.

> > TSR's are actually "easier" to write.
 Basic device drivers are very easy to write in the same way that basic TSR's are. The only real difference between the two is historically there has been better support for creating TSR's, e.g. Borland's keep routines have a lot to answer for making it far too easy for anyone to easily create "bloated" TSR's.

> > While CONFIG.SYS is being processed,
> > many of the DOS services that you generally take for granted (even very
> > basic things like writing text to the screen, manipulating files, and
> > redirection/piping) are limited or non-existent.
>
> I think this assumption is a bit too pessimistic.
I fully agree. Indeed if the exact opposite was true then it wouldn't be possible for SYS "drivers" like wrapper.sys to load TSR's, would it?

> What's probably missing, are environment variables.
 I seem to remember that in some DOS situations there may be environment variables as well, e.g. WINDIR/TMP/TEMP (set via IO.SYS) and even COMSPEC if SHELL= has already been used? I suspect it may depend on the DOS version used.

From distant memory I seem to remember that SHELL= was supposed to be the last entry in a CONFIG.SYS (as I use now limited CONFIG.SYS files I may be remembering this wrong). Still I guessed that other people probably put SHELL earlier in CONFIG.SYS files before other drivers and did a quick search returned an example in the second "MS-DOS 6+" CONFIG.SYS example on Wikipedia which shows the SHELL line before COUNTRY.SYS.

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