[GreenKeys] Tell me about TTY Line Length

[Jim Haynes]

On Thu, 16 Apr 2020, ad7i wrote:
> In testing my model 15 and 28RO, it looks like both will print 72 characters
> per line.  But buried deep in my brain, from some long forgotten place, I
> seem to recall that the max TTY line length was 68 characters.
> 
It's adjustable of course - you could in principle get 85 characters to a
line on 8-1/2 inch paper, or even more if you use 12 to the inch character
spacing.  I wish I had a time machine so I could go back and whisper in
Sterling Morton's ear to make the machine an inch wider, so it could print
the contents of an IBM tab card on one line.  With sprocket feed paper
of the period you lose an inch for the perforation strips, so 75 
characters would be the maximum possible and 72 would be a better number.

68 characters might be where you want the margin bell to ring - adjustable
too of course - for a 72 character line.  72 characters leaves you 1.3 
inches for the margins, so 0.6 inch margin on one side and 0.7 inches on
the other side.  I imagine for business letters there are esthetic reasons
for choosing the sizes of margins and then the line length follows from
that choice.