Aiken code
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The Aiken code (also known as 2421 code) is a complementary binary-coded decimal (BCD) code. A group of four bits is assigned to the decimal digits from 0 to 9 according to the following table. The code was developed by Howard Hathaway Aiken and is still used today in digital clocks, pocket calculators and similar devices[citation needed].
The Aiken code differs from the standard 8421 BCD code in that the Aiken code does not weight the fourth digit as 8 as with the standard BCD code but with 2.
The following weighting is obtained for the Aiken code: 2-4-2-1.
One might think that double codes are possible for a number, for example 1011 and 0101 could represent 5. However, here one makes sure that the digits 0 to 4 are mirror image complementary to the numbers 5 to 9.
| Aiken code | |
|---|---|
| Decimal digit | Aiken 2 4 2 1 code |
| 0 | 0 0 0 0 |
| 1 | 0 0 0 1 |
| 2 | 0 0 1 0 |
| 3 | 0 0 1 1 |
| 4 | 0 1 0 0 |
| 5 | 1 0 1 1 |
| 6 | 1 1 0 0 |
| 7 | 1 1 0 1 |
| 8 | 1 1 1 0 |
| 9 | 1 1 1 1 |
See also
Further reading
- White, Garland S. (October 1953). "Coded Decimal Number Systems for Digital Computers". Proceedings of the Institute of Radio Engineers. 41 (10). Institute of Radio Engineers (IRE): 1450–1452. doi:. eISSN . ISSN . S2CID . (3 pages)