Logo Turtle Draw
Learners are usually introduced to Logo programming through the "turtle," an icon on a computer screen which can be commanded to move around the screen and leave a trace as it goes. So, for example, the turtle can be told to move forward a hundred steps and turn ninety degrees with the commands FORWARD 100 RIGHT 90. Four such commands would have the turtle drawing a square. Programming occurs when a set of commands, such as REPEAT 4 [FORWARD 100 RIGHT 90], are defined as a procedure: TO SQUARE. Alternatively, a subprocedure TO SIDE might be defined and repeated four times.