Transcode (character encoding)
{{Short description|IBM 6-bit data transmission code}}
{{Other uses|Transcode (disambiguation)}}
{{Use dmy dates|date=May 2019|cs1-dates=y}}
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.{{cite book |last=IBM Corporation |title=Component Description: IBM 2780 Communications Terminal |year=1971 |url=http://www.bitsavers.org/pdf/ibm/2780/GA27-3005-3-2780_Data_Terminal_Description_Aug71.pdf |url-status=live |archive-url=https://web.archive.org/web/20200726231256/http://www.bitsavers.org/pdf/ibm/2780/GA27-3005-3-2780_Data_Terminal_Description_Aug71.pdf |archive-date=2020-07-26}}
Code table
| {{chset-table-header1|Six-Bit Transcode}} |
| {{chset-left1|0x}}
|{{chset-ctrl1|U+0001 START OF HEADING|{{Control code link|SOH}}}} |{{chset-cell1|U+0041 LATIN CAPITAL LETTER A|A|1}} |{{chset-cell1|U+0042 LATIN CAPITAL LETTER B|B|2}} |{{chset-cell1|U+0043 LATIN CAPITAL LETTER C|C|3}} |{{chset-cell1|U+0044 LATIN CAPITAL LETTER D|D|4}} |{{chset-cell1|U+0045 LATIN CAPITAL LETTER E|E|5}} |{{chset-cell1|U+0046 LATIN CAPITAL LETTER F|F|6}} |{{chset-cell1|U+0047 LATIN CAPITAL LETTER G|G|7}} |{{chset-cell1|U+0048 LATIN CAPITAL LETTER H|H|8}} |{{chset-cell1|U+0049 LATIN CAPITAL LETTER I|I|9}} |{{chset-ctrl1|U+0002 START OF TEXT|{{Control code link|STX}}}} |{{chset-cell1|U+002E FULL STOP|.}} |{{chset-cell1|U+2311 SQUARE LOZENGE|⌑}} |{{chset-ctrl1|U+0007 BELL|{{Control code link|BEL}}}} |{{chset-ctrl1|U+001A SUBSTITUTE|{{Control code link|SUB}}}} |{{chset-ctrl1|U+0017 END OF TRANSMISSION BLOCK|{{Control code link|ETB}}}} |
| {{chset-left1|1x}}
|{{chset-cell1|U+0026 AMPERSAND|&}} |{{chset-cell1|U+004A LATIN CAPITAL LETTER J|J}} |{{chset-cell1|U+004B LATIN CAPITAL LETTER K|K}} |{{chset-cell1|U+004C LATIN CAPITAL LETTER L|L}} |{{chset-cell1|U+004D LATIN CAPITAL LETTER M|M}} |{{chset-cell1|U+004E LATIN CAPITAL LETTER N|N}} |{{chset-cell1|U+004F LATIN CAPITAL LETTER O|O}} |{{chset-cell1|U+0050 LATIN CAPITAL LETTER P|P}} |{{chset-cell1|U+0051 LATIN CAPITAL LETTER Q|Q}} |{{chset-cell1|U+0052 LATIN CAPITAL LETTER R|R}} |{{chset-ctrl1|U+0020 SPACE|SP}} |{{chset-cell1|U+0024 DOLLAR SIGN|$}} |{{chset-cell1|U+002A ASTERISK|*}} |{{chset-ctrl1|U+001F INFORMATION SEPARATOR ONE|{{Control code link|US|IUS}}/ |{{chset-ctrl1|U+0004 END OF TRANSMISSION|{{Control code link|EOT}}}} |{{chset-ctrl1|U+0010 DATA LINK ESCAPE|{{Control code link|DLE}}}} |
| {{chset-left1|2x}}
|{{chset-cell1|U+002D HYPHEN-MINUS|Hyphen-minus |
| }}
|{{chset-cell1|U+002F SOLIDUS|/}} |{{chset-cell1|U+0053 LATIN CAPITAL LETTER S|S}} |{{chset-cell1|U+0054 LATIN CAPITAL LETTER T|T}} |{{chset-cell1|U+0055 LATIN CAPITAL LETTER U|U}} |{{chset-cell1|U+0056 LATIN CAPITAL LETTER V|V}} |{{chset-cell1|U+0057 LATIN CAPITAL LETTER W|W}} |{{chset-cell1|U+0058 LATIN CAPITAL LETTER X|X}} |{{chset-cell1|U+0059 LATIN CAPITAL LETTER Y|Y}} |{{chset-cell1|U+005A LATIN CAPITAL LETTER Z|Z}} |{{chset-ctrl1|U+001B ESCAPE|{{Control code link|ESC}}}} |{{chset-cell1|U+0027 APOSTROPHE|'}} |{{chset-cell1|U+0025 PERCENT SIGN|%}} |{{chset-ctrl1|U+0005 ENQUIRY|{{Control code link|ENQ}}}} |{{chset-ctrl1|U+0003 END OF TEXT|{{Control code link|ETX}}}} |{{chset-ctrl1|U+0009 CHARACTER TABULATION|{{Control code link|HT}}}} |
| {{chset-left1|3x}}
|{{chset-cell1|U+0030 DIGIT ZERO|0}} |{{chset-cell1|U+0031 DIGIT ONE|1}} |{{chset-cell1|U+0032 DIGIT TWO|2}} |{{chset-cell1|U+0033 DIGIT THREE|3}} |{{chset-cell1|U+0034 DIGIT FOUR|4}} |{{chset-cell1|U+0035 DIGIT FIVE|5}} |{{chset-cell1|U+0036 DIGIT SIX|6}} |{{chset-cell1|U+0037 DIGIT SEVEN|7}} |{{chset-cell1|U+0038 DIGIT EIGHT|8}} |{{chset-cell1|U+0039 DIGIT NINE|9}} |{{chset-ctrl1|U+0016 SYNCHRONOUS IDLE|{{Control code link|SYN}}}} |{{chset-cell1|U+0023 NUMBER SIGN|#}} |{{chset-cell1|U+0040 COMMERCIAL AT|@}} |{{chset-ctrl1|U+0015 NEGATIVE ACKNOWLEDGE|{{Control code link|NAK}}}} |{{chset-ctrl1|U+0019 END OF MEDIUM|{{Control code link|EM }}}} |{{chset-ctrl1|U+007F DELETE|{{Control code link|DEL}}}} |
Code table (from 2780 manual)
| class="wikitable" style="font-family: 'Courier New';"
! Character | |||
| 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 |
Devices 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)