Transcode (character encoding): Difference between revisions

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{{Short description|IBM 6-bit data transmission code}}

{{otherOther uses|Transcode (disambiguation)}}

'''Transcode''', or ''Transmission Code'', was a 6-bit plus parity [[BCD (6-bit)|BCD]] [[character encoding|character set]] which was used by [[IBM]] for a short time for [[Binary Synchronous Communications|Binary Synchronous communications]]. The [[IBM 2780]] data transmission terminal was announced with Transcode support in 1967. The [[IBM 2780#3780|IBM 3780]] data communication terminal, the 2780 successor announced in 1972, dropped Transcode support.

{{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 encoding|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 2780#3780|IBM 3780]] [[data communication]] terminal, announced in 1972, dropped Transcode support and added a "space compression" option.

Transcode was a 64 character set including twenty-six upper case alphabetic characters, ten numerics, thirteen special characters, and sixteen [[control characters]]. Characters were transmitted with [[odd parity]].<ref>{{cite book|last=IBM Corporation |title=Component Description: IBM 2780 Communications Terminal |year=1971 |url=http://computer-refuge.org/bitsavers/pdf/ibm/27xx/GA27-3005-3-2780_Data_Terminal_Description_Aug71.pdf |deadurl=yes |archiveurl=http://web.archive.org/web/20110929024649/http://computer-refuge.org/bitsavers/pdf/ibm/27xx/GA27-3005-3-2780_Data_Terminal_Description_Aug71.pdf |archivedate=September 29, 2011 }}</ref>

Transcode is a [[six-bit character code]]. It relates to IBM's [[punched card code]] but, like [[EBCDIC]], it is not [[BCD (character encoding)|BCD]]. Its 64 values consist of the 26 uppercase letters, 10 numbers, 11 symbols, [[space (character)|space]], and 16 [[control character]]s. Its 48 printable characters are <code>ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 .'-/@#$%&*⌑</code>; it cannot represent <code>,:;!?"()[]<>+^=_\`{}|~</code>. Characters are transmitted with [[odd parity]]. The 2780 cannot use the 16 control characters as data characters in Transcode mode.<ref>{{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}}</ref>

==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|[[Full stop|.]]}}

|{{chset-cell1|U+2311 SQUARE LOZENGE|[[Lozenge (shape)|⌑]]}}

|{{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|[[Ampersand|&amp;]]}}

|{{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|[[Space character|SP]]}}

|{{chset-cell1|U+0024 DOLLAR SIGN|[[Dollar sign|$]]}}

|{{chset-cell1|U+002A ASTERISK|[[Asterisk|*]]}}

|{{chset-ctrl1|U+001F INFORMATION SEPARATOR ONE|{{Control code link|US|IUS}}/<br/>{{Control code link|IUS/ITB|ITB}}|style=line-height:1}}

|{{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|[[Slash (punctuation)|/]]}}

|{{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|[[Apostrophe|']]}}

|{{chset-cell1|U+0025 PERCENT SIGN|[[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|[[Number sign|#]]}}

|{{chset-cell1|U+0040 COMMERCIAL AT|[[At sign|@]]}}

|{{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<br>&nbsp; !! [[Punched card]]<br>code !! 6-bit<br>transcode !! Hex&nbsp;

Line 27 ⟶ 109:

| I || 12-9 || &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;5&nbsp;P || 09

|-

| STX || 12-09-2 || &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;&nbsp;&nbsp;4&nbsp;&nbsp;&nbsp;P || 0A

|-

| . || 12-98-3 || &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;&nbsp;&nbsp;4&nbsp;5&nbsp;&nbsp; || 0B

|-

| &#8977;⌑ || 12-98-4 || &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;P || 0C

|-

| BEL || 0-9-8-7 || &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;3&nbsp;&nbsp;&nbsp;5&nbsp;&nbsp; || 0D

Line 37 ⟶ 119:

| Sub || 9-8-7 || &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;3&nbsp;4&nbsp;&nbsp;&nbsp;&nbsp; || 0E

|-

| ETB || 90-89-6 || &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;3&nbsp;4&nbsp;5&nbsp;P || 0F

|-

| & || 12 || &nbsp;&nbsp;&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; || 10

Line 91 ⟶ 173:

| Z || 0-9 || &nbsp;0&nbsp;&nbsp;&nbsp;2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;5&nbsp;&nbsp; || 29

|-

| ESC || 90-89-7 || &nbsp;0&nbsp;&nbsp;&nbsp;2&nbsp;&nbsp;&nbsp;4&nbsp;&nbsp;&nbsp;&nbsp; || 2A

|-

| ' || 0-8-3 || &nbsp;0&nbsp;&nbsp;&nbsp;2&nbsp;&nbsp;&nbsp;4&nbsp;5&nbsp;P || 2B

|-

| &#x25;% || 0-8-4 || &nbsp;0&nbsp;&nbsp;&nbsp;2&nbsp;3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; || 2C

|-

| ENQ || 0-9-8-5 || &nbsp;0&nbsp;&nbsp;&nbsp;2&nbsp;3&nbsp;&nbsp;&nbsp;5&nbsp;P || 2D

Line 137 ⟶ 219:

==Devices using Transcode==

* [[IBM 2701]] Data Adapter Unit.

* [[IBM 2703]] Transmission Control.

* [[IBM 2780/3780|IBM 2780]] Data Transmission Terminal.

* [[IBM System/370]] model 135 Integrated Communications Adapter (ICA).

==References==

{{Reflist}}

{{characterCharacter encodingencodings}}

[[Category:Character encoding]]

[[Category:IBM computer hardware]]