>
>
> On Mon, Mar 29, 2021 at 5:16 PM Erik E. Fair <fair-tuhs@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