A general-purpose language, Logo is widely known for its use of turtle graphics, in which commands for movement and drawing produced line graphics either on screen or with a small robot called a turtle. The language was conceived to teach concepts of programming related to Lisp and only later to enable what Papert called "body-syntonic reasoning", where students could understand, predict and reason about the turtle's motion by imagining what they would do if they were the turtle. There are substantial differences among the many dialects of Logo, and the situation is confused by the regular appearance of turtle-graphics programs that call themselves Logo.
Logo is a multi-paradigm adaptation and dialect of Lisp, a functional programming language. There is no standard Logo, but UCBLogo has the best facilities for handling lists, files, I/O, and recursion in scripts, and can be used to teach all computer science concepts, as UC Berkeley lecturer Brian Harvey did in his Computer Science Logo Style trilogy.
Logo is usually an interpreted language, although there have been developed compiled Logo dialects (such as Lhogho and Liogo). Logo is not case-sensitive but retains the case used for formatting.
Logo was created in 1967 at Bolt, Beranek and Newman (BBN), a Cambridge, Massachusetts research firm, by Wally Feurzeig, Cynthia Solomon, and Seymour Papert. Its intellectual roots are in artificial intelligence, mathematical logic and developmental psychology. The first four years of Logo research, development and teaching work was done at BBN. The first implementation of Logo, called Ghost, was written in LISP on a PDP-1. The goal was to create a mathematical land where children could play with words and sentences. Modeled on LISP, the design goals of Logo included accessible power and informative error messages. The use of virtual Turtles allowed for immediate visual feedback and debugging of graphic programming.
The first working Logo turtle robot was created in 1969. A display turtle preceded the physical floor turtle. Modern Logo has not changed too much from the basic concepts before the first turtle. The first turtle was a tethered floor roamer, not radio-controlled or wireless. At BBN Paul Wexelblat developed a turtle named Irving that had touch sensors and could move forwards, backwards, rotate, and ding its bell. The earliest year-long school users of Logo were in 1968-69 at Muzzey Jr High, Lexington MA. The virtual and physical turtles were first used by fifth graders at the Bridge School in Lexington, MA in 1970-71.