[TUHS] Remember the ed thread?

Rob Pike robpike at gmail.com
Tue Mar 30 14:30:56 AEST 2021

Night operators were known to nap on top of the 1401s. When there was a
need for more paper, they would be gently awakened.


On Tue, Mar 30, 2021 at 9:30 AM John P. Linderman <jpl.jpl at gmail.com> wrote:

>> On Mon, Mar 29, 2021 at 5:16 PM Erik E. Fair <fair-tuhs at netbsd.org>
>> wrote:
>> Line printers are distinguished not by the width of the paper but by the
>>> printer having enough print heads to print an entire line of output at a
>>> time. That speed advantage made them the preferred output device for
>>> many-page program listings, as opposed to a teleprinter terminals which
>>> were more suitable for interactive computing.
>> There were originally two styles, the drum printers which DEC sold(e.g.
>> LP20)  and the chain printers that IBM offered (e.g. 1401).  The drum had
>> all the characters in each of the 132 columns (the upper case only printers
>> were faster because the alphabet was on the drum in two places).  The
>> IBM ones has slugs on a rapidly spinning chain that was horizontal (and parallel)
>> to the line being printed.    The chain was easily replaceable by the
>> operator - which was one of the duties we would have.  When a user queued a
>> printer a set of symbols (*i.e.* the chain of the needed output
>> characters) was specified and the system queued it until the printer had
>> been properly provisioned.   For instance, CMU printed checks with a
>> special chain and film ink, so once a night the operator would configure
>> the printer, and tell the queue to print them).  Some chains were faster
>> than others, the standard one had N copies of each character.
>> In common to both schemes is that each both styles had 132 hammers and
>> when the proper character was in the position needed, the hammer fired to
>> make an impression the ribbon on the paper, which was caused the noise
>> people associated with computer printers.  The high-end IBM 1401 had a
>> hydraulic cover that came down over it and was controlled by the channel
>> processor (it would auto-open when it needed to be serviced - like a new
>> box of paper).
>> This led to the "first commandment of fancy printers": Thou shalt not
> leave thine coffee on top of the printer. -- jpl
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