Text Editor and Corrector

TECO

Original author(s)	Dan Murphy
Initial release	1962/63
Type	Text editor

TECO (/ˈtiːkoʊ/; originally an acronym for [paper] Tape editor and corrector, but later Text editor and corrector, then Text editor character oriented) is a text editor originally developed at the Massachusetts Institute of Technology (MIT) in the 1960s, after which it was modified by "just about everybody". TECO was a direct ancestor of Emacs, which was originally implemented in TECO macros.

TECO is not only an editor but also an interpreted programming language for text manipulation. Arbitrary programs (called "macros") for searching and modifying text give it great power. Unlike regular expressions, however, the language was imperative (though some versions had an "or" operator in string search).

TECO does not really have syntax; each character in a program is an imperative command, dispatched to its corresponding routine. That routine may read further characters from the program stream (giving the effect of string arguments), change the position of the "program counter" (giving the effect of control structures), or push values onto a value stack (giving the effect of nested parentheses). But there is nothing to prevent operations like jumping into the middle of a comment, since there is no syntax and no parsing.

A classic essay on computer programming, Real Programmers Don't Use Pascal, suggested that a common game for TECO fans was to enter their name as a command sequence, and then try to work out what would happen. The same essay in describing TECO coined the acronym YAFIYGI, meaning "You Asked For It You Got It" and thus being the antithesis of WYSIWYG ("What You See Is What You Get").

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