[TUHS] tabs vs spaces - entab, detab

Greg A. Woods woods at robohack.ca
Sat Mar 6 05:29:15 AEST 2021

At Fri, 5 Mar 2021 11:44:49 -0500, M Douglas McIlroy <m.douglas.mcilroy at dartmouth.edu> wrote:
Subject: [TUHS] tabs vs spaces - entab, detab
> > The reason to use tab was file size for one
> This is urban legend. The percentage of 512-byte blocks that
> tabs would save was never significant.

Using tabs to save space was definitely more than an urban legend for
some of us!  (but there is a caveat below)

When I started at UofCalgary we had a PDP-11/60 running 7th Edition
(with about 16 terminals).  It had an RX-02 mounted into the terminal
room wall (the computer room was of course on the other side of the
wall, with a nice big window so we could see the blinken lights (which
are of course very few on an 11/60, but enough to tell when it was most
busy churning the disks).

Students were strongly encouraged to buy 8-1/2" disks at the books store
and off-load anything they were not directly working on at any given
time.  (And when we upgraded to a VAX 11/780 with BSD, disk quotas were
implemented as soon as possible.)

Some of us found that we could fit considerably more data on those disks
if we made sure we used tabs everywhere possible.  We also obviously
learned to have a "clean" target in our makefiles and to be sure to use
it before we archived anything!

However I think we were probably using tar, not a filesystem, on the
floppies so that would of course have been what allowed for greater
savings.  I don't remember many of the details, though I do remember
there was a program to reserve and "lock" the drive, and I think it
changed the ownership of the device file(s) to the user requesting the

As for the size of tabs, well I seem to recall students also traded
tabstop setup files for various kinds of terminals so that each could
see code indentations at their own preferred size.  (Maybe this was done
more on the Multics system though, and/or it was in the pre-Vi days when
we used a custom full-screen editor called Fred.)

					Greg A. Woods <gwoods at acm.org>

Kelowna, BC     +1 250 762-7675           RoboHack <woods at robohack.ca>
Planix, Inc. <woods at planix.com>     Avoncote Farms <woods at avoncote.ca>

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