IBM CMS dumpfile idiocy

Rich Alderson RichA at
Wed Dec 16 13:59:30 CST 2015

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 Alderson
Vintage Computing Sr. Systems Engineer
Living Computer Museum
2245 1st Avenue S
Seattle, WA 98134

mailto:RichA at

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