Bi-quinary coded decimal

Bi-quinary coded decimal is a numeral encoding scheme used in many abacuses and in some early computers, including the Colossus.[2] The term bi-quinary indicates that the code comprises both a two-state (bi) and a five-state (quinary) component. The encoding resembles that used by many abacuses, with four beads indicating the five values either from 0 through 4 or from 5 through 9 and another bead indicating which of those ranges (which can alternatively be thought of as +5).

Biquinary code example[1]
Reflected biquinary code
Japanese abacus. The right side represents 1,234,567,890 in bi-quinary: each column is one digit, with the lower beads representing "ones" and the upper beads "fives".

Several human languages, most notably Fula and Wolof also use biquinary systems. For example, the Fula word for 6, jowi e go'o, literally means five [plus] one. Roman numerals use a symbolic, rather than positional, bi-quinary base, even though Latin is completely decimal.

The Korean finger counting system Chisanbop uses a bi-quinary system, where each finger represents a one and a thumb represents a five, allowing one to count from 0 to 99 with two hands.

One advantage of one bi-quinary encoding scheme on digital computers is that it must have 2 bits set (one in the binary field and one in the quinary field), providing a built in checksum to verify if the number is valid or not. (Stuck bits happened frequently with computers using mechanical relays.)

Examples edit

Several different representations of bi-quinary coded decimal have been used by different machines. The two-state component is encoded as one or two bits, and the five-state component is encoded using three to five bits. Some examples are:

Two bi bits: 0 5 and five quinary bits: 0 1 2 3 4, with error checking.
Exactly one bi bit and one quinary bit is set in a valid digit. In the pictures of the front panel below and in close-up, the bi-quinary encoding of the internal workings of the machine are evident in the arrangement of the lights – the bi bits form the top of a T for each digit, and the quinary bits form the vertical stem.
(the machine was running when the photograph was taken and the active bits are visible in the close-up and just discernible in the full panel picture)
Value 05-01234 bits[1]
IBM 650 front panel
Close-up of IBM 650 indicators
0 10-10000
1 10-01000
2 10-00100
3 10-00010
4 10-00001
5 01-10000
6 01-01000
7 01-00100
8 01-00010
9 01-00001
One quinary bit (tube) for each of 1, 3, 5, and 7 - only one of these would be on at the time.
The fifth bi bit represented 9 if none of the others were on; otherwise it added 1 to the value represented by the other quinary bit.
(sold in the two models UNIVAC 60 and UNIVAC 120)
Value 1357-9 bits
0 0000-0
1 1000-0
2 1000-1
3 0100-0
4 0100-1
5 0010-0
6 0010-1
7 0001-0
8 0001-1
9 0000-1
One bi bit: 5, three binary coded quinary bits: 4 2 1[4][5][6][7][8][9] and one parity check bit
Value p-5-421 bits
0 1-0-000
1 0-0-001
2 0-0-010
3 1-0-011
4 0-0-100
5 0-1-000
6 1-1-001
7 1-1-010
8 0-1-011
9 1-1-100
One bi bit: 5, three Johnson counter-coded quinary bits and one parity check bit
Value p-5-qqq bits
0 1-0-000
1 0-0-001
2 1-0-011
3 0-0-111
4 1-0-110
5 0-1-000
6 1-1-001
7 0-1-011
8 1-1-111
9 0-1-110

See also edit

References edit

  1. ^ a b Ledley, Robert Steven; Rotolo, Louis S.; Wilson, James Bruce (1960). "Part 4. Logical Design of Digital-Computer Circuitry; Chapter 15. Serial Arithmetic Operations; Chapter 15-7. Additional Topics". Digital Computer and Control Engineering (PDF). McGraw-Hill Electrical and Electronic Engineering Series (1 ed.). New York, US: McGraw-Hill Book Company, Inc. (printer: The Maple Press Company, York, Pennsylvania, US). pp. 517–518. ISBN 0-07036981-X. ISSN 2574-7916. LCCN 59015055. OCLC 1033638267. OL 5776493M. SBN 07036981-X. ISBN 978-0-07036981-8. ark:/13960/t72v3b312. Archived (PDF) from the original on 2021-02-19. Retrieved 2021-02-19. p. 518: […] The use of the biquinary code in this respect is typical. The binary part (i.e., the most significant bit) and the quinary part (the other 4 bits) are first added separately; then the quinary carry is added to the binary part. If a binary carry is generated, this is propagated to the quinary part of the next decimal digit to the left. […] [1] (xxiv+835+1 pages)
  2. ^ "Why Use Binary? - Computerphile". YouTube. 2015-12-04. Archived from the original on 2021-12-12. Retrieved 2020-12-10.
  3. ^ Stibitz, George Robert; Larrivee, Jules A. (1957). Written at Underhill, Vermont, US. Mathematics and Computers (1 ed.). New York, US / Toronto, Canada / London, UK: McGraw-Hill Book Company, Inc. p. 105. LCCN 56-10331. (10+228 pages)
  4. ^ Berger, Erich R. (1962). "1.3.3. Die Codierung von Zahlen". Written at Karlsruhe, Germany. In Steinbuch, Karl W. (ed.). Taschenbuch der Nachrichtenverarbeitung (in German) (1 ed.). Berlin / Göttingen / New York: Springer-Verlag OHG. pp. 68–75. LCCN 62-14511.
  5. ^ Berger, Erich R.; Händler, Wolfgang (1967) [1962]. Steinbuch, Karl W.; Wagner, Siegfried W. (eds.). Taschenbuch der Nachrichtenverarbeitung (in German) (2 ed.). Berlin, Germany: Springer-Verlag OHG. LCCN 67-21079. Title No. 1036.
  6. ^ Steinbuch, Karl W.; Weber, Wolfgang; Heinemann, Traute, eds. (1974) [1967]. Taschenbuch der Informatik - Band II - Struktur und Programmierung von EDV-Systemen (in German). Vol. 2 (3 ed.). Berlin, Germany: Springer-Verlag. ISBN 3-540-06241-6. LCCN 73-80607. {{cite book}}: |work= ignored (help)
  7. ^ Dokter, Folkert; Steinhauer, Jürgen (1973-06-18). Digital Electronics. Philips Technical Library (PTL) / Macmillan Education (Reprint of 1st English ed.). Eindhoven, Netherlands: The Macmillan Press Ltd. / N. V. Philips' Gloeilampenfabrieken. doi:10.1007/978-1-349-01417-0. ISBN 978-1-349-01419-4. SBN 333-13360-9. Retrieved 2020-05-11.[permanent dead link] (270 pages) (NB. This is based on a translation of volume I of the two-volume German edition.)
  8. ^ Dokter, Folkert; Steinhauer, Jürgen (1975) [1969]. Digitale Elektronik in der Meßtechnik und Datenverarbeitung: Theoretische Grundlagen und Schaltungstechnik. Philips Fachbücher (in German). Vol. I (improved and extended 5th ed.). Hamburg, Germany: Deutsche Philips GmbH. p. 50. ISBN 3-87145-272-6. (xii+327+3 pages) (NB. The German edition of volume I was published in 1969, 1971, two editions in 1972, and 1975. Volume II was published in 1970, 1972, 1973, and 1975.)
  9. ^ a b Savard, John J. G. (2018) [2006]. "Decimal Representations". quadibloc. Archived from the original on 2018-07-16. Retrieved 2018-07-16.

Further reading edit