Editing TECO (text editor) (section)

==Description==
TECO is not only an editor but also an [[interpreter (computer software)|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 programming|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.

TECO ignores [[letter case|case]] and [[whitespace character|whitespace]] (except [[tab character|tab]], which is an insertion command).<ref>{{cite web 
|quote=<tab>text$, Inserts specified text preceded by a tab.
|url=http://www.avanthar.com/healyzh/teco/TecoPocketGuide.html
|title=TECO Pocket Guide}}</ref>

A satirical 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" (in contrast to [[WYSIWYG]]).