Bi-quinary coded decimal

Bi-quinary coded decimal is a <a href="/facts/Numeral_system/1KKlG4nd">numeral encoding scheme</a> used in many <a href="/facts/Abacus/ThMQBsel">abacuses</a> and in some <a href="/facts/Early_computer/83xXSmuW">early computers</a>, notably the <a href="/facts/Colossus_computer/pbkHLPwp">Colossus</a>. 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).
Several human languages, most notably <a href="/facts/Fula_language/NhqBrdYM">Fula</a> and <a href="/facts/Wolof_language/5DSHvUYc">Wolof</a> also use biquinary systems. For example, the Fula word for 6, jowi e go'o, literally means five [plus] one. <a href="/facts/Roman_numerals/7BA8nn78">Roman numerals</a> use a symbolic, rather than positional, bi-quinary base, even though <a href="/facts/Latin/pM3Kge85">Latin</a> is completely decimal.
The Korean finger counting system <a href="/facts/Chisanbop/N02RFI7o">Chisanbop</a> 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 two bits set (one in the binary field and one in the quinary field), providing a built-in <a href="/facts/Checksum/AqxQ0I8g">checksum</a> to verify if the number is valid or not. (Stuck bits happened frequently with computers using <a href="/facts/Relay/NQcb9usW">mechanical relays</a>.)

Bi-quinary coded decimal open-in-new

Bi-quinary coded decimal