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From: torkil@psivax.UUCP (Torkil Hammer)
Newsgroups: comp.lang.misc,comp.software-eng
Subject: Re: :=
Message-ID: <2877@psivax.UUCP>
Date: 7 Oct 89 00:38:34 GMT
References: <1989Oct3.182931.518@jarvis.csri.toronto.edu>
Reply-To: torkil@psivax.UUCP (Torkil Hammer)
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 48

In article <1989Oct3.182931.518@jarvis.csri.toronto.edu> malton@csri.toronto.edu (Andrew Malton) writes:
#Apparently := to express the assignment operation was used faute de mieux
#in Algol since the arrow <--- originally chosen for this purpose wasn't
#available on teletypes. Does anyone know a reference for this story?
#Or, is it folklore.
#
Originally Algol was for publication and used several non-typewriter fonts.
For example, reserved words (begin, end and such) were in boldface.

But TeletypE (tm), No Sir! no you don't in Algol.
By the time it became a programming language the major driving forces
were all European (Denmark, England, Holland) and teletypes are an
American specialty.  We used Flexowriters, some bitchy pieces of machinery
as noisy and clunky and breakdown prone as teletypes but with 2 major
advantages.  The first was that Flexo used 8 row paper tape compared to
teletype 5.  The second was that there was a key for sHIFT INTO UPPER
CASE AND WITHOUT THAT FACILITY ALGOL WOULD HAVE LOOKED LIKE FORTRAN,
AND PASCAL LIKE ALGOL, AND C LIKE PASCAL, AND ADA LIKE C, AND COMPUTER
PROGRAMS WOULD ALL HAVE LOOKED LIKE AMERICAN IMMIGRATION FORMS, AND WE WOULD
ALL BE SCREAMING ACROSS THE NET. BUT THE LOWer case code fixed that, and
let's all rejoice.  (The case shift code was sometimes punched a character
or two after it should have appeared but that went with the territory...)

Flexo codes included some characters not available on the typewriter, but
not the back arrow.  I think they just forgot to put it in.  There was a
subscript 10 as one character to indicate power of 10 in numeric constants.
There was a big sloppy X to use for multiplication.  There was even one for
shift between red and black typewriter ribbon.  Artistic we were.
Error messages brought us in the red and compilation OK brought us back.
There was a non-paper advancing key that gave the _ in lower case and the
| in upper.  It was useful for constructing reserved words, commonly
defined as underscored words, and exponentiation which was also forgotten
(should have been upper case of backarrow) - simulated as the |^ combination
printed in one space.  The quotes weren't there either, but they were done
as |< and |> and |<< which sort of looked funny.  It also forced printer
driver software to do double takes unless we really wanted to look at
_B_E_G_I_N _I_N_T_E_G_E_R N; - and that in turn often annoyed the printer
hardware which was specified to be able to do doubles but really wasn't
expecting to actually have to do it after the selloff demo.  (Line printers
were American, upper case only, and Fortran rarely does double takes).

After the Flexowriter came the Bima, which was a quieter version with a much
prettier font, but even more breakdown prone and couldn't be fixed with
whatever was lying around at 4 am, but that's a whole 'nother story.

You'll get that some other Friday evening.  Bye now

torkil