From Wikipedia, the free encyclopedia
Bi-quinary coded decimal is a numeral encoding scheme used in many abacuses and in some early computers, including the Colossus. The term bi-quinary indicates that the code comprises both a two-state (bi) and a five-state (quinary) component.
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 or five bits. 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); in the picture of the front panel below, the bi-quinary encoding of the internal workings of the machine are evident in the arrangement of the lights (active bits are just visible)
| Value |
05-01234 Bits |
IBM 650 front panel
|
| 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 |
| Value |
13579 bits |
| 0 |
00000 |
| 1 |
10000 |
| 2 |
10001 |
| 3 |
01000 |
| 4 |
01001 |
| 5 |
00100 |
| 6 |
00101 |
| 7 |
00010 |
| 8 |
00011 |
| 9 |
00001 |
| 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 |
- Univac LARC – 4 bits (one ‘bi’ bit: 5 and three ring counter coded ‘quinary’ bits) with 1 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 |
[edit] See also
