16 Dec
2015
16 Dec
'15
11:59 a.m.
From: Paul Koning
Sent: Wednesday, December 16, 2015 7:58 AM
IBM standard labels are older than ANSI. Then again,
IBM (in OS/360 at
least) had something they called "ANSI label" that were not actually ANSI at
all. They used "8 bit ASCII" which was a bizarre code created from standard
7 bit ASCII by moving one or two of the bits (bit 6 to bit 7? I don't
remember).
Ah, yes, PSW bit 12. Re-used for entirely different purpose on the System/370.
ASCII was defined as a 7-bit code in 1963, prior to the announcement of the
System/360 family. Unlike every other vendor, who thought that sticking a
leading zero on the 7-bit character codes was sufficient, IBM proposed an 8-bit
extended ASCII in which the defined 7-bit codes mapped to 8-bit codes thus:
....... ==> ..0.....
and extended codes were shaped like ..1..... ! Not even IBM used that, so I
doubt that any tape marked AL ever had anything but 0....... ASCII characters
on it.
(Used to eff around with mag tapes on 360/370 systems all the time when I was
younger, but I got better.)
Rich
Rich Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134
mailto:RichA at LivingComputerMuseum.org
http://www.LivingComputerMuseum.org/