LOGO is a 4 letter word that starts with L.

A lisp-like language for teaching programming, noted for its "turtle graphics" used to draw geometric shapes. LOGO was developed in 1966-1968 by a group at bolt, beranek & newman headed by Wally Fuerzeig <fuerzeig@bbn.com> and including Seymour Papert <seymour@media.mit.edu>.

There are Logo interpreters for macintosh, unix, ibm pc, x window system, and many PCs. Implmentations include berkeley logo, mswlogo.