Baudot code

The 5-bit Baudot code was the first widely used binary character encoding. Émile Baudot developed it in 1870 for use in telegraph and teletypewriter applications. In order to accommodate 26 letters, 10 digits, and some punctuation in five bits, it used shift codes to switch between the "letters" set and the "figures" set of characters. This technique is still used in some modern character encodings. Several variants of Baudot, including the CCITT-approved ITA2, were used over the next century.

[Baudot character code reference]