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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.^[ref]

A named procedure can package this 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.

Turtle graphics draws through commands interpreted relative to a moving cursor's position and heading. A forward command moves along the current heading, a turn changes it, and pen state determines whether motion leaves a mark. The picture is the trace of a sequence of state changes, making geometric reasoning executable.^[ref]

In Logo, repeat 4 [forward 100 right 90] draws a square and returns to the original heading and position. For a regular $n$-sided polygon, each exterior turn is $360/n$ degrees, so the total turning is one full revolution. The same procedure works from a different initial position or heading, illustrating how local commands avoid specifying every absolute coordinate.