17 Jul
2014
17 Jul
'14
10:01 p.m.
On Jul 17, 2014, at 20:56 , Chuck Guzis <cclist at sydex.com> wrote:
The DELs/Rubouts were included to allow time for the
carriage return-linefeed at the end of line on TTYs. Usually, one rubout would do, but
two was safe.
It doesn't matter to modern electronic equipment--the rubouts are non-printing.
Do paper tape BASIC interpreters pay any attention to the DELs when they're loading a
program, or are they just there so that the tape can be printed legibly on teletype-style
console?
Can other nonprinting characters be used in place of the DEL, like a NUL or a 0x80 (NUL
after the MSB is stripped off)? I notice that the DELs weaken those 38-year-old tapes
quite a bit.
I'm asking about these little trivialities because I'll probably write a little
utility for archiving and punching tapes, and I want to get the details right. I've
added some preliminary stuff to my silly paper tape renderer package at
https://github.com/NF6X/papertape but I'll probably write a standalone python script
later, with built-in features to strip or add mark parity, add/remove leaders, punch a
human-readable title at the beginning of a tape, etc.
That GNT 4604 reader really zips through the tape quickly. I put a box in front of it to
catch the tape as it belches out of the reader, but it's still time-consuming to
rewind the tape after reading it. The machine orients the tape the opposite way from my 33
ASR, so the "top" markings on the tape are wrong when swapping a tape punched on
one machine to the other one's reader. Let's see, according to the ECMA standard,
the GNT 4604 is "right" and the 33 ASR is "wrong".
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/