8 Jun
2023
8 Jun
'23
6:13 p.m.
On Jun 8, 2023, at 1:18 PM, Adrian Godwin
<artgodwin(a)gmail.com> wrote:
...
I've seen mylar tape used in a tiny loop where it controlled the movements of a
printer platen. I don't recall now whether it was used for horizontal or vertical
space - my recollection was the latter but it was a long time ago.
I don't know why it wasn't controlled by ASCII - a good bit of the character set
is dedicated to print head control. I think a different tape had to be installed to match
the program that was being run. The machine was used for accountancy in about 1975, It was
a bit like a large LA120 (but included the calculating part) and made by the french
Logabax company.
Many line printers used a "VFD" tape (vertical format definition?) which is a
12-channel tape with one row per line on the paper. The idea was that you could tell the
printer "skip to channel N" and it would advance the paper until a hole in that
channel was seen. By convention, channel 1 marks the top of the page, and in fact
typically that position was punched all the way across so a skip to an "unused"
channel would not produce runaway paper. Channels other than 1 would be used for custom
forms, where it would save time to skip across part of the form rather than advancing line
by line to the desired spot.
If you only ever used regular size paper this stuff wouldn't be obvious, but an
operator who had to handle other forms, like checks or label stock or anything else that
wasn't just plain 60/66 line pages, would have to change the paper along with the
matching format tape. Some printers had small local memories that could be downloaded
with the form definition tape data, avoiding the need for the operator to switch the tape
manually.
paul