On Tue, 20 Nov 2018 17:13:33 -0600, Paul Gilmartin wrote: >On Tue, 20 Nov 2018 16:07:24 -0600, Tom Marchant wrote about UNPK:
>>It sets the zone bits to F when in EBCDIC mode and to 5 when in ASCII mode. >> >5? I would have expected 3: Yes, in retrospect, I would have expected 3 too. Remember that the ASCII standard was first published in June of 1963, some two years after the start of the System/360 project, and just 10 months before the announcement. You might find this interesting: https://retrocomputing.stackexchange.com/questions/4920/whats-the-deal-with-system-360s-usascii-mode In the document describing the ASCII standard, http://worldpowersystems.com/ARCHIVE/codes/X3.4-1963/index.html an 8-bit form was explicitly rejected (see page 7). The design considerations for System/360 were documented in the paper Architecture of the IBM System/360 by Amdahl, Blaauw, and Brooks, first published in the IBM Journal of Research and development: http://www.ece.ucdavis.edu/~vojin/CLASSES/EEC272/S2005/Papers/IBM360-Amdahl_april64.pdf And the System/360 Principles of operation is on Bitsavers: http://bitsavers.trailing-edge.com/pdf/ibm/360/princOps/ Each of the above contains a chart depicting the IBM extension of ASCII to an 8-bit code. By the -6 version, the USASCII-8 chart has this footnote: Current activities in committees under the auspices of the United States of America Standards Institute may result in changes to the characters and/or structure of the eight-bit representation of USASCII devised by the Institute. Such changes may cause the eight-bit representation of USASCII implemented in System/360 (USASCII-8) to be different from a future USA Standard. Since a difference of this nature may eventually lead to a modification of System/360, it is recommended that users avoid: (1) operation with PSW bit 12 set to 1, and (2) the use of any sign codes in decimal data other than those preferred for EBCDIC. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
