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Bi-quinary coded decimal is a numeral system used in some old computers. Bi-quinary means two (bi) and five (quinary) code. In bi-quinary coded decimal, numbers are represented as decimal digits, and each digit is represented a group of bits.
There are several different representations of bi-quinary coded decimal that have been used by different machines, some examples are:
- IBM 650 - 7 bits (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 set in a valid digit)
- UNIVAC Solid State - 4 bits (one "bi" bit: 5 and three binary coded "quinary" bits: 4 2 1) with 1 parity check bit
