Transcode (character encoding)
IBM 6-bit data transmission code
Six-Bit Transcode, or Six-Bit Transmission Code, was, for a few years, one of the three character sets used by IBM for Binary Synchronous Communications. Transmission using 6-bit Transcode had higher throughput than transmission using 8-bit EBCDIC or ASCII, provided that the data to be transmitted used a limited set of 48 characters.
The IBM 2780 data transmission terminal was announced with Transcode support in 1967. Its successor, the IBM 3780 data communication terminal, announced in 1972, dropped Transcode support and added a "space compression" option.
Transcode is a six-bit character code. It relates to IBM's punched card code but, like EBCDIC, it is not BCD. Its 64 values consist of the 26 uppercase letters, 10 numbers, 11 symbols, space, and 16 control characters. Its 48 printable characters are ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 .'-/@#$%&*⌑; it cannot represent ,:;!?"()[]<>+^=_\`{}|~. Characters are transmitted with odd parity. The 2780 cannot use the 16 control characters as data characters in Transcode mode.
01Code table
02Code table (from 2780 manual)
| Character | Punched card code | 6-bit transcode | Hex |
|---|---|---|---|
| SOH | 12-9-1 | P | 00 |
| A | 12-1 | 5 | 01 |
| B | 12-2 | 4 | 02 |
| C | 12-3 | 4 5 P | 03 |
| D | 12-4 | 3 | 04 |
| E | 12-5 | 3 5 P | 05 |
| F | 12-6 | 3 4 P | 06 |
| G | 12-7 | 3 4 5 | 07 |
| H | 12-8 | 2 | 08 |
| I | 12-9 | 2 5 P | 09 |
| STX | 12-9-2 | 2 4 P | 0A |
| . | 12-8-3 | 2 4 5 | 0B |
| ⌑ | 12-8-4 | 2 3 P | 0C |
| BEL | 0-9-8-7 | 2 3 5 | 0D |
| Sub | 9-8-7 | 2 3 4 | 0E |
| ETB | 0-9-6 | 2 3 4 5 P | 0F |
| & | 12 | 1 | 10 |
| J | 11-1 | 1 5 P | 11 |
| K | 11-2 | 1 4 P | 12 |
| L | 11-3 | 1 4 5 | 13 |
| M | 11-4 | 1 3 P | 14 |
| N | 11-5 | 1 3 5 | 15 |
| O | 11-6 | 1 3 4 | 16 |
| P | 11-7 | 1 3 4 5 P | 17 |
| Q | 11-8 | 1 2 P | 18 |
| R | 11-9 | 1 2 5 | 19 |
| Space | no punch | 1 2 4 | 1A |
| $ | 11-8-3 | 1 2 4 5 P | 1B |
| * | 11-8-4 | 1 2 3 | 1C |
| US | 11-9-8-7 | 1 2 3 5 P | 1D |
| EOT | 9-7 | 1 2 3 4 P | 1E |
| DLE | 12-11-9-8-1 | 1 2 3 4 5 | 1F |
| - | 11 | 0 | 20 |
| / | 0-1 | 0 5 P | 21 |
| S | 0-2 | 0 4 P | 22 |
| T | 0-3 | 0 4 5 | 23 |
| U | 0-4 | 0 3 P | 24 |
| V | 0-5 | 0 3 5 | 25 |
| W | 0-6 | 0 3 4 | 26 |
| X | 0-7 | 0 3 4 5 P | 27 |
| Y | 0-8 | 0 2 P | 28 |
| Z | 0-9 | 0 2 5 | 29 |
| ESC | 0-9-7 | 0 2 4 | 2A |
| ' | 0-8-3 | 0 2 4 5 P | 2B |
| % | 0-8-4 | 0 2 3 | 2C |
| ENQ | 0-9-8-5 | 0 2 3 5 P | 2D |
| ETX | 12-9-3 | 0 2 3 4 P | 2E |
| HT | 12-9-5 | 0 2 3 4 5 | 2F |
| 0 | 0 | 0 1 P | 30 |
| 1 | 1 | 0 1 5 | 31 |
| 2 | 2 | 0 1 4 | 32 |
| 3 | 3 | 0 1 4 5 P | 33 |
| 4 | 4 | 0 1 3 | 34 |
| 5 | 5 | 0 1 3 5 P | 35 |
| 6 | 6 | 0 1 3 4 P | 36 |
| 7 | 7 | 0 1 3 4 5 | 37 |
| 8 | 8 | 0 1 2 | 38 |
| 9 | 9 | 0 1 2 5 P | 39 |
| SYN | 9-2 | 0 1 2 4 P | 3A |
| # | 8-3 | 0 1 2 4 5 | 3B |
| @ | 8-4 | 0 1 2 3 P | 3C |
| NAK | 9-8-5 | 0 1 2 3 5 | 3D |
| EM | 11-9-8-1 | 0 1 2 3 4 | 3E |
| DEL | 12-9-7 | 0 1 2 3 4 5 P | 3F |
03Devices using Transcode
- IBM 2701 Data Adapter Unit
- IBM 2703 Transmission Control
- IBM 2780 Data Transmission Terminal
- IBM System/370 model 135 Integrated Communications Adapter (ICA)
Sources and credits
This article is adapted from the Wikipedia article “Transcode (character encoding)”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Fathomly is not affiliated with or endorsed by the Wikimedia Foundation. Spotted a problem? Tell us.