These 65 control codes were carried over to Unicode. Extended ASCII sets defined by ISO 8859 added the codes 128 through 159 as control characters, this was primarily done so that if the high bit was stripped it would not change a printing character to a C0 control code, but there have been some assignments here, in particular NEL. The code 127 ( DEL) is also a control character. But the number of non-standard variations in use is large, especially among printers, where technology has advanced far faster than any standards body can possibly keep up with.Īll entries in the ASCII table below code 32 (technically the C0 control code set) are of this kind, including CR and LF used to separate lines of text. Several standards exist for these sequences, notably ANSI X3.64. For example, the sequence of code 27, followed by the printable characters "[2 10H", would cause a Digital Equipment Corporation VT100 terminal to move its cursor to the 10th cell of the 2nd line of the screen. The mechanism was invented by Bob Bemer, the father of ASCII. Specifically, they used ASCII code 27 (escape), followed by a series of characters called a "control sequence" or "escape sequence". It quickly became possible and inexpensive to interpret sequences of codes to perform a function, and device makers found a way to send hundreds of device instructions. This was because early terminals had very primitive mechanical or electrical controls that made any kind of state-remembering API quite expensive to implement, thus a different code for each and every function looked like a requirement. There were quite a few control characters defined (33 in ASCII, and the ECMA-48 standard adds 32 more).
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