4 Feb
2021
4 Feb
'21
3:10 a.m.
On Feb 3, 2021, at 12:07, John Cowan
<cowan(a)ccil.org> wrote:
On the 36-bit PDP-10, things were better: the sign bit was mostly ignored and five 7-bit
ASCII characters were packed into each word, again with NUL padding. (Line editors turned
on the sign bit to indicate that this word held an explicit ASCII line number.)
The PDP-7, 9, and 15 used 18-bit words, but used the same "5/7 IOPS ASCII"
packing strategy. That is, five 7-bit ASCII characters were packed into a word pair.
Unfortunately, they didn't have the convenient character manipulation instructions
found on the PDP-10, so programmers had to do shifts, masks, etc. Grumble.
-r