Split octal

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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. [1] (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. ^ "As I recall some DEC utilities supported 'split octal' which was base 8 on 8 bit... | Hacker News". Archived from the original on 2020-07-27.
  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. ^ The 8080/Z-80 assembly language : Techniques for improved programming. 1981. ISBN 9780471081241.
  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, [2] Archived 23 July 2011 at the Wayback Machine, 29 September 2001
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