Baudot and CCITT Character Codes

Interactive Baudot/CCITT code demonstration applet, click here.

The Baudot code, invented in 1870 and patented in 1874 by J. Baudot is a five-bit binary code. Originally used in wireless telegraphy as a replacement for Morse Code. It was adopted as an official international code by the CCITT (Comité Consultatif International Téléphonique et Télégraphique: International Consultative Committee for Telephony and Telegraphy), and is now known as CCITT-1. The word Baud, a unit of transmission speed equal to one physical bit per second, is named after Monsieur Baudot and his code.

Naturally, a 5-bit code only allows 32 different symbols, which is not even enough for letters and digits. The Baudot code includes two 30-symbol character sets, and two Shift symbols, the shift symbols are used to shift between the two character sets, thereby allowing for 60 different symbols.

It was very common for Baudot code to be used in conjunction with a paper tape punch and reader; teletype machines often had an integral paper tape unit. The tape was punched with five holes (or absences of holes) across its width to indicate the zeros and ones of each characetr's code. A smaller sixth hole was punched between the third and fourth bits for purely mechanical reasons: it allowed the paper to be pulled through the punch (and later the reader) very cheaply using a small toothed wheel.

This graphic shows the string "BAUDOT" punched on tape using the CCITT-2 code.

The two character sets are called LTRS and FIGS. Each new message starts in the LTRS character set; code FIGS changes to the FIGS character set, and code LTRS changes back again.

In 1901 the code was rearranged by someone called Murray. The rearrangement had a purpose: The characters that appeared most frequently were given codes that invoved the fewest transitions between 0 and 1. This minimises wear on the sending equipment, which was all electro-mechanical with lots of moving parts. The new code was accepted as CCITT-2, or International Alphabet Two. When anyone uses the name "Baudot Code", they most probably mean CCITT-2, not the original.

Equipment made by different manufacturers could send the five bits of each character in different orders. The only orders ever used for the five bits were 12345 and 54321, i.e.normal and reverse orders, and it is not absolutely clear that the CCITT standard really made a distinction. So both orderings are given in all the tables that follow.

Revised Baudot (Murray), CCITT-2, Alphabetical Order

Common Binary	Common Decimal	LTRS	FIGS	Reverse Binary	Reverse Decimal
`00011`	`3`	`A`	`-`	`11000`	`24`
`11001`	`25`	`B`	`?`	`10011`	`19`
`01110`	`14`	`C`	`:`	`01110`	`14`
`01001`	`9`	`D`	`$`	`10010`	`18`
`00001`	`1`	`E`	`3`	`10000`	`16`
`01101`	`13`	`F`	`!`	`10110`	`22`
`11010`	`26`	`G`	`&`	`01011`	`11`
`10100`	`20`	`H`	`#`	`00101`	`5`
`00110`	`6`	`I`	`8`	`01100`	`12`
`01011`	`11`	`J`	`4`	`11010`	`26`
`01111`	`15`	`K`	`(`	`11110`	`30`
`10010`	`18`	`L`	`)`	`01001`	`9`
`11100`	`28`	`M`	`.`	`00111`	`7`
`01100`	`12`	`N`	`,`	`00110`	`6`
`11000`	`24`	`O`	`9`	`00011`	`3`
`10110`	`22`	`P`	`0`	`01101`	`13`
`10111`	`23`	`Q`	`1`	`11101`	`29`
`01010`	`10`	`R`	`'`	`01010`	`10`
`00101`	`5`	`S`	`BEL`	`10100`	`20`
`10000`	`16`	`T`	`5`	`00001`	`1`
`00111`	`7`	`U`	`7`	`11100`	`28`
`11110`	`30`	`V`	`;`	`01111`	`15`
`10011`	`19`	`W`	`2`	`11001`	`25`
`11101`	`29`	`X`	`/`	`10111`	`23`
`10101`	`21`	`Y`	`6`	`10101`	`21`
`10001`	`17`	`Z`	`"`	`10001`	`17`
`00010`	`2`	`LF`	`LF`	`01000`	`8`
`00100`	`4`	`SP`	`SP`	`00100`	`4`
`01000`	`8`	`CR`	`CR`	`00010`	`2`
`11011`	`27`	`FIGS`	`FIGS`	`11011`	`27`
`11111`	`31`	`LTRS`	`LTRS`	`11111`	`31`

The special symbols SP, CR, LF, and BEL are:

SP Space
CR Carriage Return - move print head back to beginning of line
LF Line Feed - Move paper up by one line
BEL Sound bell or other audible alarm.

"Newline" is really a two character sequence: CR, LF.

Example: The message "May 24th" is encoded as 11100 00011 10101 00100 11011 10011 01011 11111 10000 10100.

Revised Baudot (Murray), CCITT-2, Code Order

Common Order

Reversed Order

Binary	Decimal	LTRS	FIGS
`00000`	`0`	`(not used)`
`00001`	`1`	`E`	`3`
`00010`	`2`	`LF`	`LF`
`00011`	`3`	`A`	`-`
`00100`	`4`	`SP`	`SP`
`00101`	`5`	`S`	`BEL`
`00110`	`6`	`I`	`8`
`00111`	`7`	`U`	`7`
`01000`	`8`	`CR`	`CR`
`01001`	`9`	`D`	`$`
`01010`	`10`	`R`	`'`
`01011`	`11`	`J`	`4`
`01100`	`12`	`N`	`,`
`01101`	`13`	`F`	`!`
`01110`	`14`	`C`	`:`
`01111`	`15`	`K`	`(`
`10000`	`16`	`T`	`5`
`10001`	`17`	`Z`	`"`
`10010`	`18`	`L`	`)`
`10011`	`19`	`W`	`2`
`10100`	`20`	`H`	`#`
`10101`	`21`	`Y`	`6`
`10110`	`22`	`P`	`0`
`10111`	`23`	`Q`	`1`
`11000`	`24`	`O`	`9`
`11001`	`25`	`B`	`?`
`11010`	`26`	`G`	`&`
`11011`	`27`	`FIGS`	`FIGS`
`11100`	`28`	`M`	`.`
`11101`	`29`	`X`	`/`
`11110`	`30`	`V`	`;`
`11111`	`31`	`LTRS`	`LTRS`

Binary	Decimal	LTRS	FIGS
`00000`	`0`	`(not used)`
`10000`	`16`	`E`	`3`
`01000`	`8`	`LF`	`LF`
`11000`	`24`	`A`	`-`
`00100`	`4`	`SP`	`SP`
`10100`	`20`	`S`	`BEL`
`01100`	`12`	`I`	`8`
`11100`	`28`	`U`	`7`
`00010`	`2`	`CR`	`CR`
`10010`	`18`	`D`	`$`
`01010`	`10`	`R`	`'`
`11010`	`26`	`J`	`4`
`00110`	`6`	`N`	`,`
`10110`	`22`	`F`	`!`
`01110`	`14`	`C`	`:`
`11110`	`30`	`K`	`(`
`00001`	`1`	`T`	`5`
`10001`	`17`	`Z`	`"`
`01001`	`9`	`L`	`)`
`11001`	`25`	`W`	`2`
`00101`	`5`	`H`	`#`
`10101`	`21`	`Y`	`6`
`01101`	`13`	`P`	`0`
`11101`	`29`	`Q`	`1`
`00011`	`3`	`O`	`9`
`10011`	`19`	`B`	`?`
`01011`	`11`	`G`	`&`
`11011`	`27`	`FIGS`	`FIGS`
`00111`	`7`	`M`	`.`
`10111`	`23`	`X`	`/`
`01111`	`15`	`V`	`;`
`11111`	`31`	`LTRS`	`LTRS`

Original Baudot, CCITT-1, Alphabetical Order

Common Binary	Common Decimal	LTRS	FIGS	Reverse Binary	Reverse Decimal
`00000`	`0`	`NUL`	`NUL`	`00000`	`0`
`00100`	`4`	`A`	`1`	`00100`	`4`
`10010`	`18`	`B`	`8`	`01001`	`9`
`10110`	`22`	`C`	`9`	`01101`	`13`
`11110`	`30`	`D`	`0`	`01111`	`15`
`01000`	`8`	`E`	`2`	`00010`	`2`
`11010`	`26`	`F`	`(nat)`	`01011`	`11`
`01010`	`10`	`G`	`7`	`01010`	`10`
`01110`	`14`	`H`	`(nat)`	`01110`	`14`
`11000`	`24`	`I`	`(nat)`	`00011`	`3`
`00110`	`6`	`J`	`6`	`01100`	`12`
`00111`	`7`	`K`	`(`	`11100`	`28`
`01111`	`15`	`L`	`=`	`11110`	`30`
`01011`	`11`	`M`	`)`	`11010`	`26`
`11011`	`27`	`N`	`£`	`11011`	`27`
`11100`	`28`	`O`	`5`	`00111`	`7`
`11111`	`31`	`P`	`+`	`11111`	`31`
`10111`	`23`	`Q`	`/`	`11101`	`29`
`10011`	`19`	`R`	`-`	`11001`	`25`
`10001`	`17`	`S`	`(nat)`	`10001`	`17`
`10101`	`21`	`T`	`(nat)`	`10101`	`21`
`10100`	`20`	`U`	`4`	`00101`	`5`
`11101`	`29`	`V`	`'`	`10111`	`23`
`11001`	`25`	`W`	`?`	`10011`	`19`
`01001`	`9`	`X`	`(nat)`	`10010`	`18`
`10000`	`16`	`Y`	`3`	`00001`	`1`
`01101`	`13`	`Z`	`:`	`10110`	`22`
`00001`	`1`	`LTRS`	`LTRS`	`10000`	`16`
`00010`	`2`	`FIGS`	`FIGS`	`01000`	`8`
`00011`	`3`	`END`	`END`	`11000`	`24`

The special symbols NUL and (nat) are:

NUL A null code, effectively equivalent to a space,
(nat) National: these characters would be different for users in different countries.

"Newline" does not exist. This code was replaced in 1901, there was no such thing as a teletype. Receptions were decoded and transcribed by hand, so the idea of explicit line breaks did not arise.

Original Baudot, CCITT-1, Code Order

Common Order

Reversed Order

Binary	Decimal	LTRS	FIGS
`00000`	`0`	`NUL`	`NUL`
`00001`	`1`	`LTRS`	`LTRS`
`00010`	`2`	`FIGS`	`FIGS`
`00011`	`3`	`END`	`END`
`00100`	`4`	`A`	`1`
`00101`	`5`	`-`	`.`
`00110`	`6`	`J`	`6`
`00111`	`7`	`K`	`(`
`01000`	`8`	`E`	`2`
`01001`	`9`	`X`	`(nat)`
`01010`	`10`	`G`	`7`
`01011`	`11`	`M`	`)`
`01100`	`12`	`/`	`(nat)`
`01101`	`13`	`Z`	`:`
`01110`	`14`	`H`	`(nat)`
`01111`	`15`	`L`	`=`
`10000`	`16`	`Y`	`3`
`10001`	`17`	`S`	`(nat)`
`10010`	`18`	`B`	`8`
`10011`	`19`	`R`	`-`
`10100`	`20`	`U`	`4`
`10101`	`21`	`T`	`(nat)`
`10110`	`22`	`C`	`9`
`10111`	`23`	`Q`	`/`
`11000`	`24`	`I`	`(nat)`
`11001`	`25`	`W`	`?`
`11010`	`26`	`F`	`(nat)`
`11011`	`27`	`N`	`£`
`11100`	`28`	`O`	`5`
`11101`	`29`	`V`	`'`
`11110`	`30`	`D`	`0`
`11111`	`31`	`P`	`+`

Binary	Decimal	LTRS	FIGS
`00000`	`0`	`NUL`	`NUL`
`10000`	`16`	`LTRS`	`LTRS`
`01000`	`8`	`FIGS`	`FIGS`
`11000`	`24`	`END`	`END`
`00100`	`4`	`A`	`1`
`10100`	`20`	`-`	`.`
`01100`	`12`	`J`	`6`
`11100`	`28`	`K`	`(`
`00010`	`2`	`E`	`2`
`10010`	`18`	`X`	`(nat)`
`01010`	`10`	`G`	`7`
`11010`	`26`	`M`	`)`
`00110`	`6`	`/`	`(nat)`
`10110`	`22`	`Z`	`:`
`01110`	`14`	`H`	`(nat)`
`11110`	`30`	`L`	`=`
`00001`	`1`	`Y`	`3`
`10001`	`17`	`S`	`(nat)`
`01001`	`9`	`B`	`8`
`11001`	`25`	`R`	`-`
`00101`	`5`	`U`	`4`
`10101`	`21`	`T`	`(nat)`
`01101`	`13`	`C`	`9`
`11101`	`29`	`Q`	`/`
`00011`	`3`	`I`	`(nat)`
`10011`	`19`	`W`	`?`
`01011`	`11`	`F`	`(nat)`
`11011`	`27`	`N`	`£`
`00111`	`7`	`O`	`5`
`10111`	`23`	`V`	`'`
`01111`	`15`	`D`	`0`
`11111`	`31`	`P`	`+`