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Path: utzoo!watmath!clyde!burl!ulysses!harpo!decvax!ucbvax!ucbtopaz!unisoft!phil
From: phil@unisoft.UUCP
Newsgroups: net.arch
Subject: Re: RE: IBM-ASCII-C-Etc
Message-ID: <286@unisoft.UUCP>
Date: Tue, 15-May-84 19:49:38 EDT
Article-I.D.: unisoft.286
Posted: Tue May 15 19:49:38 1984
Date-Received: Thu, 17-May-84 02:13:30 EDT
References: <2587@ncsu.UUCP> <627@ariel.UUCP>, <1915@rlgvax.UUCP>
Organization: UniSoft Corp., Berkeley
Lines: 26

>> > The original IBM 360 assembler that we used in Kingston, NY in
>> > 1966 was actually a cross assembler which ran on IBSYS on a
>> > 7094 across the road.  We used a three tape rotation system.
>> > This is probably why the 360 had an ASCII bit in the PSW.
>> 
>> But didn't the 7094 use BCDIC (the six-bit predecessor to EBCDIC) rather
>> than ASCII?  There was probably an ASCII bit there because IBM wanted to
>> be able to support 8-bit ASCII when it came out - 7-bit ASCII was already
>> out (or coming out soon), and there was an 8-bit version in the works - but
>> it turned out the final version of 8-bit ASCII was not going to be what
>> IBM expected it to be and not what the 360 implemented.  For that reason,
>> and because converting all the 360 hardware and software to ASCII would
>> have been a major undertaking, IBM canned the ASCII mode in the 370.
>> 
>>	 Guy Harris
>> 	{seismo,ihnp4,allegra}!rlgvax!guy

No no. IBM provided the ASCII bit in the PSW to allow the packed decimal
instructions (and a few other instructions of the same ilk) to handle
ASCII character data to/from numeric computations. This bit was used
in the new 370's to indicate new modes of machine supervisor state
operation. IBM announced at the time that it took a survey of customers
to find out who was using the ASCII bit and found nobody was. Thus,
since bits in the PSW were getting in short supply, they resused it.
There was never any intention by IBM to convert to ASCII, nor was
this bit anything more than a numeric character conversion aid.