Syllabic octal and split octal are two similar notations for 8-bit and 16-bit

octal number The octal numeral system, or oct for short, is the base-8 number system, and uses the digits 0 to 7. This is to say that 10octal represents eight and 100octal represents sixty-four. However, English, like most languages, uses a base-10 number ...

s, respectively, used in some historical contexts.

Syllabic octal

''Syllabic octal'' is an 8-bit octal number representation that was used by

English Electric N.º UIC: 9094 110 1449-3 (Takargo Rail) The English Electric Company Limited (EE) was a British industrial manufacturer formed after the Armistice of 11 November 1918, armistice of World War I by amalgamating five businesses which, during th ...

in conjunction with their

KDF9 KDF9 was an early British 48-bit computer designed and built by English Electric (which in 1968 was merged into International Computers Limited (ICL)). The first machine came into service in 1964 and the last of 29 machines was decommissioned ...

machine in the mid-1960s. Although the word '

byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...

' had been coined by the designers of the

IBM 7030 Stretch The IBM 7030, also known as Stretch, was IBM's first transistorized supercomputer. It was the fastest computer in the world from 1961 until the first CDC 6600 became operational in 1964."Designed by Seymour Cray, the CDC 6600 was almost three tim ...

for a group of eight

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...

s, it was not yet well known, and English Electric used the word '

syllable A syllable is a unit of organization for a sequence of speech sounds typically made up of a syllable nucleus (most often a vowel) with optional initial and final margins (typically, consonants). Syllables are often considered the phonological "bu ...

' for what is now called a byte.

Machine code In computer programming, machine code is any low-level programming language, consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). Each instruction causes the CPU to perform a very ...

programming used an unusual form of

octal The octal numeral system, or oct for short, is the radix, base-8 number system, and uses the Numerical digit, digits 0 to 7. This is to say that 10octal represents eight and 100octal represents sixty-four. However, English, like most languages, ...

, 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'' (also known as 'slob-octal' or 'slob' notation,). 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 Heathkit is the brand name of kits and other electronic products produced and marketed by the Heath Company. The products over the decades have included electronic test equipment, high fidelity home audio equipment, television receivers, amateu ...

's PAM8 and portions of

HDOS HDOS is an early microcomputer operating system, originally written for the Heathkit H8 computer system and later also available for the Heathkit H89 and Zenith Z-89 computers. The author was Heath Company employee Gordon Letwin, who later was an ...

for the

Heathkit H8 Heathkit's H8 is an Intel 8080A-based microcomputer sold in kit form starting in 1977. The H8 is similar to the S-100 bus computers of the era, and like those machines is often used with the CP/M operating system on floppy disk. The main dif ...

in the late 1970s (and sometimes up to the present). It was also used by

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...

(DEC). Following this convention, 16-bit numbers were split into two 8-bit numbers printed separately in octal, that is base 8 on 8-bit boundaries: 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 (/), dot (.), colon (:) hyphen (-), or hash mark (#). Most

mini The Mini is a small, two-door, four-seat car, developed as ADO15, and produced by the British Motor Corporation (BMC) and its successors, from 1959 through 2000. Minus a brief hiatus, original Minis were built for four decades and sold during ...

- and micro-computers used either straight octal (377 was followed by 400) or

hexadecimal In mathematics and computing, the hexadecimal (also base-16 or simply hex) numeral system is a positional numeral system that represents numbers using a radix (base) of 16. Unlike the decimal system representing numbers using 10 symbols, hexa ...

. With the introduction of the optional HA8-6

Z80 The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples were ...

processor replacement for the

8080 The Intel 8080 (''"eighty-eighty"'') is the second 8-bit microprocessor designed and manufactured by Intel. It first appeared in April 1974 and is an extended and enhanced variant of the earlier 8008 design, although without binary compatibili ...

board, the front-panel keyboard got a new set of labels and hexadecimal notation was used instead of octal. Through tricky number alignment the

HP-16C The HP-16C Computer Scientist is a programmable pocket calculator that was produced by Hewlett-Packard between 1982 and 1989. It was specifically designed for use by computer programmers, to assist in debugging. It is a member of the HP Voyager ...

and other

Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...

RPN calculators supporting

base conversion Positional notation (or place-value notation, or positional numeral system) usually denotes the extension to any base of the Hindu–Arabic numeral system (or decimal system). More generally, a positional system is a numeral system in which the ...

can implicitly support numbers in split octal as well.

References

{{reflist, refs= {{anchor, Beard-1997{{cite magazine , title=The KDF9 Computer — 30 Years On , author-first=Bob , author-last=Beard , magazine=

Resurrection Resurrection or anastasis is the concept of coming back to life after death. In a number of religions, a dying-and-rising god is a deity which dies and is resurrected. Reincarnation is a similar process hypothesized by other religions, which ...

- The Bulletin of the Computer Conservation Society , issn=0958-7403 , publisher=

Computer Conservation Society The Computer Conservation Society (CCS) is a British organisation, founded in 1989. It is under the joint umbrella of the British Computer Society (BCS), the London Science Museum and the Manchester Museum of Science and Industry. Overview The ...

(CCS) , volume= , number=18 , date=Autumn 1997 , orig-date=1996-10-01 , pages=7–15 , 11, url=http://www.cs.man.ac.uk/CCS/Archive/Resurrection/pdf/res18.pdf , access-date=2020-07-27 , url-status=live , archive-url=https://web.archive.org/web/20200727140754/http://www.cs.man.ac.uk/CCS/Archive/Resurrection/pdf/res18.pdf , archive-date=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".) {{cite web , title=Architecture of the English Electric KDF9 computer. , version=Version 1 , date=September 2009 , publisher=

(CCS) , id=CCS-N4X2 , url=http://www.ourcomputerheritage.org/ccs-n2x2.pdf , access-date=2020-07-27 , url-status=live , archive-url=https://web.archive.org/web/20200404195007/http://www.ourcomputerheritage.org/ccs-n2x2.pdf , archive-date=2020-07-27 (NB. Refers to Beard's 1997 #Beard-1997, article.) {{cite book , title=Director - Manual , type=Flowchart , publisher=

, date=c. 1960s , work=KDF 8 , pages=40–49 , url=http://sw.ccs.bcs.org/KDF9/directorManuals/20090803114911646.pdf , access-date=2020-07-27 , url-status=live , archive-url=https://web.archive.org/web/20200727222921/http://sw.ccs.bcs.org/KDF9/directorManuals/20090803114911646.pdf , archive-date=2020-07-27 (10 pages) (NB. Mentions the term "syllabic octal".) {{cite web , title=As I recall some DEC utilities supported 'split octal' which was base 8 on 8 bit boundaries , author-first=Chuck , author-last=McManis , date=2016-12-09 , work=Hacker News: Combinator , url=https://news.ycombinator.com/item?id=13140527 , access-date=2022-07-17 , url-status=live , archive-url=https://web.archive.org/web/20200727003857/https://news.ycombinator.com/item?id=13140527 , archive-date=2020-07-27 {{cite book , title=Control Data 8092 TeleProgrammer: Programming Reference Manual , date=1964 , id=IDP 107a , publisher=

Control Data Corporation Control Data Corporation (CDC) was a mainframe and supercomputer firm. CDC was one of the nine major United States computer companies through most of the 1960s; the others were IBM, Burroughs Corporation, DEC, NCR, General Electric, Honeywel ...

, location=Minneapolis, Minnesota, USA , url=http://bitsavers.org/pdf/cdc/809x/IDP107a_8092pgmRef_1964.pdf , access-date=2020-07-27 , url-status=live , archive-url=https://web.archive.org/web/20200525053524/http://bitsavers.org/pdf/cdc/809x/IDP107a_8092pgmRef_1964.pdf , archive-date=2020-05-25 {{cite magazine , title=Control the World! (Or at Least a Few Analog Points) , author-first=Steve , author-last=Ciarcia , author-link=Steve Ciarcia , location=Glastonbury, Connecticut, USA , magazine=

BYTE The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...

– the small systems journal , issn=0360-5280 , publisher= BYTE Publications Inc. , date=September 1977 , volume=2 , number=9 , pages=30, 32, 34, 36, 38–40, 42–43, 156–158, 160–161 57–158, url=https://vintageapple.org/byte/pdf/197709_Byte_Magazine_Vol_02-09_Music_and_Computers.pdf , access-date=2020-07-31 , url-status=live , archive-url=https://web.archive.org/web/20190720194118/https://vintageapple.org/byte/pdf/197709_Byte_Magazine_Vol_02-09_Music_and_Computers.pdf , archive-date=2019-07-20 {{cite magazine , title=Building the Heath H8 Computer , author-first=Paul R. , author-last=Poduska , location=Nashua, New Hampshire, USA , magazine=

– the small systems journal , issn=0360-5280 , publisher= BYTE Publications Inc. , date=March 1979 , volume=4 , number=3 , pages=12–13, 124–130, 132–134, 136–138, 140 29, 138, url=https://worldradiohistory.com/Archive-Byte/70s/Byte-1979-03.pdf , access-date=2020-07-31 , url-status=live , archive-url=https://web.archive.org/web/20200708173537/https://worldradiohistory.com/Archive-Byte/70s/Byte-1979-03.pdf , archive-date=2019-07-08 {{cite book , title=The 8080/Z-80 Assembly Language: Techniques for Improved Programming , author-first=Alan R. , author-last=Miller , date=1981 , orig-date=June 1980 , edition=1 , location=New York, USA , publisher= John Wiley & Sons, Inc. , isbn=0-471-08124-8 , lccn=80-21492 , id=ark:/13960/t4zg8792b. {{ISBN, 978-0-471-08124-1 , url=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 , access-date=2022-07-17 (1+x+319+2 pages) {{cite web , title=A8008 8008 (1975) cross-assembler A8008 8008 (1975) cross-assembler , date=2019-10-02 , author-first=Herbert "Herb" R. , author-last=Johnson , url=http://www.retrotechnology.com/restore/a8008.html , access-date=2020-07-31 , url-status=live , archive-url=https://web.archive.org/web/20200207034842/http://www.retrotechnology.com/restore/a8008.html , archive-date=2020-02-07 {{cite book , title=Introduction to number systems , chapter=39. Split-Octal Concept , author-first=Forest , author-last=Belt , publisher=Computer Diagnostics , date= , pages=48–50 , url=https://f01.justanswer.com/LVyCWET7/b0802.pdf , access-date=2020-07-31 , url-status=live , archive-url=https://web.archive.org/web/20200731211259/https://f01.justanswer.com/LVyCWET7/b0802.pdf , archive-date=2020-07-31 (iv+56 pages) {{cite web , title={31} Binary, Decimal Octal, Split Octal, and HEX , author-first=Craig , author-last=Andrews , work=Bits Of The Golden Age , type=Educational video , date=2020 , url=https://www.youtube.com/watch?v=9v2OiicrzrQ , access-date=2022-07-17 {{cite web , title=H-8 Technical details , author-first=Dave , author-last=Wallace , date=2011-07-23 , orig-date=2001-09-29, 2000 , url=http://davidwallace2000.home.comcast.net/~davidwallace2000/h8/technical.htm#z80%20cpu , url-status=dead , archive-url=https://web.archive.org/web/20110723052102/http://davidwallace2000.home.comcast.net/~davidwallace2000/h8/technical.htm#z80%20cpu , archive-date=2011-07-23 {{cite web , title=hp16 and split octal conversion , date=2021-12-02 , orig-date=2021-12-01 , author1=Roland57 , author-first2=Jean François , author-last2=Garnier , work=The Museum of HP Calculators (MoHPC) , url=https://www.hpmuseum.org/forum/thread-17777-post-154980.html , access-date=2022-07-17 , url-status=live , archive-url=https://web.archive.org/web/20220717073142/https://www.hpmuseum.org/forum/thread-17777-post-154980.html , archive-date=2022-07-17 , quote= ��Before you write a program on the hp16 to do the conversion, just put a zero between the two bytes, e.g. A9oC2 hex. Conversion to octal gives 251o302, the split octal value (with "o" als the digit zero to separate the two bytes). Same works for octal to hex. 377o377 octal to hex gives FFoFF ��Also usable on other machines with base conversion such as the 32S/ SII, the 42S or the 41C with Advantage ROM. It works because 3 hex digits are 12 bits, exactly 4 oct digits. ��} Early microcomputers Binary arithmetic Positional numeral systems

Syllabic octal

Split octal

See also

References