Logo (source code)
= Logo
{c}
<Logo> is a <programming language> with procedures, lists and interactive evaluation, often used to make algorithmic ideas visible through <turtle graphics>. The turtle has a position and heading; motion commands can draw a line while changing that state. For example, `repeat 4 [forward 100 right 90]` draws a square and returns to the initial heading. Each turn is an exterior angle, so a regular $n$-gon uses turns of $360/n$ degrees.<Berkeley Logo 6.2 User Manual by Brian Harvey>[Graphics and Control Structures, FORWARD, RIGHT and REPEAT]{ref}
A named procedure can package this <machine instruction>[instruction] pattern and accept a side length as a parameter. Repeated calls and recursive procedures then produce more elaborate drawings without storing every line explicitly. The language also manipulates words and lists; turtle drawing is a useful experimental interface for studying programs, rather than the entire language.
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