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Cyhist Apr 10 1997 A
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Date: Thu, 10 Apr 1997 09:50:26 PDT
Reply-To: "CYHIST Community Memory: Discussion list on the History of
Cyberspace" <CYHIST@MAELSTROM.STJOHNS.EDU> Sender: "CYHIST Community Memory: Discussion list on the History of
Cyberspace" <CYHIST@MAELSTROM.STJOHNS.EDU> From: "Laurence I. Press" <lpress@ISI.EDU>
Subject: 1401 trivia
In-Reply-To: Your message of Thu, 10 Apr 1997 01:00:10 -0400
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Community Memory: Discussion List on the History of Cyberspace ______________________________________________________________________
>I believe there was an 8th bit -- the record mark and that the word mark was used to end fields in a record and the record mark to end the record.
I recall the record mark as being a special character that was used to delimit records on mag tape.
There was a parity bit, but that was invisible to programmers. There were only 6 data bits -- giving the BCD code of 64 symbols. ASCII, with its 7-bit code came later. (The 1401 did not distinguish between upper and lower case -- the line printer (1403) was upper-case only). The card code was also single-case -- the cards had 80 columns and 12 rows. The top three rows were designated "zone" rows, and a character consisted of one of 3 "zone" punches plus one of the remaining "field" rows. (These were the same cards and codes as used in unit-record machines which the 1401 often replaced).
>way of determining the length of variable length operands was completely different from that of the 1401.
For sure, but there was a recognition that both two-address, core-core instructions were useful. In that sense it took both the 7xxx and 14xx lines into account.
>I'm pretty sure the encodings for the 1401 and 1410 were identical, because we used a 1401 to create mag tape input to a 1410 and I don't recall any
Yes -- I worked on an OS for the 1410.
>translation issues. Somebody is likely to point out that the addressing schemes were not the same in the two machines and this is true. The 1401 used three characters to encode a five-digit address, whereas the 1410 used five.
One quibble -- the 1401 address space was limited to 16k. As I recall, the two high-order bits in the first and third characters of the address were used to determine a block of 1k with the lower-order bits of the three characters designating the address within the block.
>I can't imagine that anybody would want to know about this piece of arcane trivia, so if you want the lecture you'll have to let me know.
I think it is kind of fun -- wierd, huh. It would be nice if one could reclaim the space used to store this junk, and use it for something useful. At least I have forgotten the op codes :-).
Lar
______________________________________________________________________
Reply-To: "CYHIST Community Memory: Discussion list on the History of
Cyberspace" <CYHIST@MAELSTROM.STJOHNS.EDU> Sender: "CYHIST Community Memory: Discussion list on the History of
Cyberspace" <CYHIST@MAELSTROM.STJOHNS.EDU> From: "Laurence I. Press" <lpress@ISI.EDU>
Subject: 1401 trivia
In-Reply-To: Your message of Thu, 10 Apr 1997 01:00:10 -0400
______________________________________________________________________
Community Memory: Discussion List on the History of Cyberspace ______________________________________________________________________
>I believe there was an 8th bit -- the record mark and that the word mark was used to end fields in a record and the record mark to end the record.
I recall the record mark as being a special character that was used to delimit records on mag tape.
There was a parity bit, but that was invisible to programmers. There were only 6 data bits -- giving the BCD code of 64 symbols. ASCII, with its 7-bit code came later. (The 1401 did not distinguish between upper and lower case -- the line printer (1403) was upper-case only). The card code was also single-case -- the cards had 80 columns and 12 rows. The top three rows were designated "zone" rows, and a character consisted of one of 3 "zone" punches plus one of the remaining "field" rows. (These were the same cards and codes as used in unit-record machines which the 1401 often replaced).
>way of determining the length of variable length operands was completely different from that of the 1401.
For sure, but there was a recognition that both two-address, core-core instructions were useful. In that sense it took both the 7xxx and 14xx lines into account.
>I'm pretty sure the encodings for the 1401 and 1410 were identical, because we used a 1401 to create mag tape input to a 1410 and I don't recall any
Yes -- I worked on an OS for the 1410.
>translation issues. Somebody is likely to point out that the addressing schemes were not the same in the two machines and this is true. The 1401 used three characters to encode a five-digit address, whereas the 1410 used five.
One quibble -- the 1401 address space was limited to 16k. As I recall, the two high-order bits in the first and third characters of the address were used to determine a block of 1k with the lower-order bits of the three characters designating the address within the block.
>I can't imagine that anybody would want to know about this piece of arcane trivia, so if you want the lecture you'll have to let me know.
I think it is kind of fun -- wierd, huh. It would be nice if one could reclaim the space used to store this junk, and use it for something useful. At least I have forgotten the op codes :-).
Lar
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