Text processing

In computing, the term text processing refers to the discipline of mechanizing the creation or manipulation of electronic text. Text usually refers to all the alphanumeric characters specified on the keyboard of the person performing the mechanization, but in general text here means the abstraction layer that is one layer above the standard character encoding of the target text. The term processing refers to automated (or mechanized) processing, as opposed to the same manipulation done manually.

Text processing involves computer commands which invoke content, content changes, and cursor movement, for example to

The text processing of a regular expression is a virtual editing machine, having a primitive programming language that has named registers (identifiers), and named positions in the sequence of characters comprising the text. Using these the "text processor" can, for example, mark a region of text, and then move it. The text processing of a utility is a filter program, or filter. These two mechanisms comprise text processing.

Since the standardized markup such as ANSI escape codes are generally invisible to the editor, they comprise a set of transitory properties that become at times indistinguishable from word processing. But the definite distinctions from word processing are that text processing proper:

In this way markup such as font and color are not really a distinguishing factor, because the character sequences that affect font and color are simply standard characters inserted automatically by a background text processing mode, made to work transparently by compliant text editors, yet becoming otherwise visible as text processing commands when that mode is not in effect. So text processing is defined most basically (but not entirely) around the visual characters (or graphemes) rather than the standard, yet invisible characters.

The development of computer text processing started in earnest with Kleene's formalizing what is a regular language. Such regular expressions could then became a mini-program, complete with a compilation process, available to perform any edit, once that language was extended. Similarly, filters are extended by evolving particular options.

...
Wikipedia