Background
The binary-coded decimal scheme described in this article is the most common encoding, but there are many others. The method here can be referred to as Simple Binary-Coded Decimal (SBCD) or BCD 8421. In the headers to the table, the '8 4 2 1', etc., indicates the weight of each bit shown; note that in the fifth column two of the weights are negative. Both ASCII and EBCDIC character codes for the digits are examples of zoned BCD, and are also shown in the table.
The following table represents decimal digits from 0 to 9 in various BCD systems:
| Digit |
BCD 8 4 2 1 |
Excess-3 or Stibitz Code |
BCD 2 4 2 1 or Aiken Code |
BCD 8 4 −2 −1 |
IBM 702 IBM 705 IBM 7080 IBM 1401 8 4 2 1 |
ASCII 0000 8421 |
EBCDIC 0000 8421 |
|---|---|---|---|---|---|---|---|
| 0 | 0000 | 0011 | 0000 | 0000 | 1010 | 0011 0000 | 1111 0000 |
| 1 | 0001 | 0100 | 0001 | 0111 | 0001 | 0011 0001 | 1111 0001 |
| 2 | 0010 | 0101 | 0010 | 0110 | 0010 | 0011 0010 | 1111 0010 |
| 3 | 0011 | 0110 | 0011 | 0101 | 0011 | 0011 0011 | 1111 0011 |
| 4 | 0100 | 0111 | 0100 | 0100 | 0100 | 0011 0100 | 1111 0100 |
| 5 | 0101 | 1000 | 1011 | 1011 | 0101 | 0011 0101 | 1111 0101 |
| 6 | 0110 | 1001 | 1100 | 1010 | 0110 | 0011 0110 | 1111 0110 |
| 7 | 0111 | 1010 | 1101 | 1001 | 0111 | 0011 0111 | 1111 0111 |
| 8 | 1000 | 1011 | 1110 | 1000 | 1000 | 0011 1000 | 1111 1000 |
| 9 | 1001 | 1100 | 1111 | 1111 | 1001 | 0011 1001 | 1111 1001 |
Read more about this topic: Binary-coded Decimal
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