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From: joe@fluke.UUCP (Joe Kelsey)
Newsgroups: net.cog-eng
Subject: Re: re: tops-20 command 'language'
Message-ID: <1088@vax3.fluke.UUCP>
Date: Tue, 23-Aug-83 11:51:37 EDT
Article-I.D.: vax3.1088
Posted: Tue Aug 23 11:51:37 1983
Date-Received: Wed, 24-Aug-83 12:34:55 EDT
References: sask.290, <1447@shark.UUCP> <212@cbosgd.UUCP>
Organization: John Fluke Mfg. Co., Everett, Wash
Lines: 47

It has always been my opinion that the "best" system to work on would
be one that included the command completion and recognition
capabilities of TWENEX (TENEX/TOPS-20), the hirearchical HELP facility
from VMS in a UNIX environment.

Mark mentioned that he didn't know how the notion of PATH would fit
into a command completion environment - well it works just fine in
TOPS-20!  TOPS-20 logical names are much more flexible than those of
VMS in that a logical name can include multiple directories - in effect
a PATH specification.  This works just fine if you define the logical
name SYS: to be whatever your favorite PATH is.  Command completion
works such that if a builtin command does not match your typein, then
the EXEC searches the SYS: path (first using your local definition,
then using the system definition), for an executable file whose name
either matches your typein or can be completed to match your typein,
depending on context.  Thus, TOPS-20 has always had the UNIX feature of
being able to "create" new commands by simply naming the executable
file, and including the directory where the file resides in your
definition of SYS: (or by including DSK: (e.g. ".") in the path).

I have also found that TOPS-20 was one of the more pleasant systems to
administer.  From a systems programming standpoint, I would rank
TOPS-20 ahead of UNIX, simply because DEC is good at producing reams of
documentation, which is still sorely lacking for UNIX.  Command
completion in TOPS-20 is not limited to just the EXEC (shell), but is
available to any and all user programs who want to take advantage of
the COMND jsys (system call).  It would not be in the UNIX spirit to
add a system call to do this, but you could certainly design a facility
for compiling this kind of interface into programs (some combination of
lex and yacc with probably a few mods to the kernel) to provide a more
consistent user interface.

People haven't mentioned one of the more recent innovations in TOPS-20,
PCL (Programmable Command Language) from CMU.  PCL provides a naive
user access to all of the command completion facilities and an easy way
to extend the EXEC in a consistent manner.  PCL is an ALGOL-like
language with integers and strings which is compiled by the EXEC to
produce new commands.  I would really like to see some sort of facility
like this available on UNIX, if only for the fact that it would really
encourage people to use a consistent user interface - something that
UNIX sorely lacks!

Well enough rambling for now.  I'm no longer associated with a TOPS-20
system, and with the demise of Project Jupiter, it looks like DEC is
giving up on TOPS-20 as well.  Sigh.  I can live with VMS and UNIX, but
my heart belongs to the -20.

/Joe