Split octal

Syllabic octal and split octal are two similar notations for 8-bit and 16-bit octal numbers, respectively, used in some historical contexts.

Syllabic octal

Syllabic octal is an 8-bit octal number representation that was used by English Electric in conjunction with their KDF9 machine in the mid-1960s.

Although the word 'byte' had been coined by the designers of the IBM 7030 Stretch for a group of eight bits, it was not yet well known, and English Electric used the word 'syllable' for what is now called a byte.

Machine code programming used an unusual form of octal, known locally as 'bastardized octal'. It represented 8 bits with three octal digits but the first digit represented only the two most-significant bits, whilst the others the remaining two groups of three bits each. A more polite colloquial name was 'silly octal', derived from the official name which was syllabic octal[1] (also known as 'slob-octal' or 'slob' notation,[2][3]).

This 8-bit notation was similar to the later 16-bit split octal notation.

Split octal

Split octal is an unusual address notation used by Heathkit's PAM8 and portions of HDOS for the Heathkit H8 in the late 1970s (and sometimes up to the present).[4][5] It was also used by Digital Equipment Corporation (DEC).

Following this convention, 16-bit numbers were split into two 8-bit numbers printed in octal: the first location was "000.000" and the location after "000.377" was "001.000".

In order to distinguish numbers in split-octal notation from ordinary 16-bit octal numbers, the two digit groups were often separated by a slash (/),[6] dot (.),[7] colon (:)[8] hyphen (-),[9] or hash mark (#).[10][11]

Most mini- and micro-computers used either straight octal (377 was followed by 400) or hexadecimal. With the introduction of the optional HA8-6 Z80 processor replacement for the 8080 board, the front-panel keyboard got a new set of labels and hexadecimal notation was used instead of octal.[12]

See also

References
  1. Director - Manual (PDF) (Flowchart). English Electric. c. 1960s. Archived (PDF) from the original on 2020-07-27. Retrieved 2020-07-27. (NB. Mentions the term "syllabic octal".)
  2. Beard, Bob (Autumn 1997) [1996-10-01]. "The KDF9 Computer — 30 Years On" (PDF). Resurrection - The Bulletin of the Computer Conservation Society. No. 18. Computer Conservation Society (CCS). pp. 7–15 [9, 11]. ISSN 0958-7403. Archived (PDF) from the original on 2020-07-27. Retrieved 2020-07-27. (NB. This is an edited version of a talk given to North West Group of the Society at the Museum of Science and Industry, Manchester, UK on 1996-10-01. It mentions the term "slob" and "slob-octal" as equivalent to "syllabic octal".)
  3. "Architecture of the English Electric KDF9 computer" (PDF). Version 1. Computer Conservation Society (CCS). September 2009. CCS-N4X2. Archived (PDF) from the original on 2020-07-27. Retrieved 2020-07-27. (NB. Refers to Beard's 1997 article.)
  4. https://web.archive.org/web/20200727003857/https://news.ycombinator.com/item?id=13140527
  5. Control Data 8092 TeleProgrammer: Programming Reference Manual (PDF). Minneapolis, Minnesota, USA: Control Data Corporation. 1964. IDP 107a. Archived (PDF) from the original on 2020-05-25. Retrieved 2020-07-27.
  6. Ciarcia, Steve (September 1977). "Control the World! (Or at Least a Few Analog Points)" (PDF). BYTE – the small systems journal. Vol. 2 no. 9. Glastonbury, CT, USA: BYTE Publications Inc. pp. 30, 32, 34, 36, 38–40, 42–43, 156–158, 160–161 [157–158]. ISSN 0360-5280. Archived (PDF) from the original on 2019-07-20. Retrieved 2020-07-31.
  7. Poduska, Paul R. (March 1979). "Building the Heath H8 Computer" (PDF). BYTE – the small systems journal. Vol. 4 no. 3. Nashua, New Hampshire, USA: BYTE Publications Inc. pp. 12–13, 124–130, 132–134, 136–138, 140 [129, 138]. ISSN 0360-5280. Archived (PDF) from the original on 2019-07-08. Retrieved 2020-07-31.
  8. https://archive.org/stream/8080_and_Z-80_Assembly_Language_Techniques_1981_John_Wiley_and_Sons/8080_and_Z-80_Assembly_Language_Techniques_1981_John_Wiley_and_Sons_djvu.txt
  9. Belt, Forest. "39. Split-Octal Concept". Introduction to number systems (PDF). Computer Diagnostics. pp. 48–50. Archived (PDF) from the original on 2020-07-31. Retrieved 2020-07-31. (iv+56 pages)
  10. Johnson, Herbert "Herb" R. (2019-10-02). "A8008 8008 (1975) cross-assembler A8008 8008 (1975) cross-assembler". Archived from the original on 2020-02-07. Retrieved 2020-07-31.
  11. https://www.youtube.com/watch?v=9v2OiicrzrQ
  12. Dave Wallace, Archived 23 July 2011 at the Wayback Machine, 29 September 2001
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.