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Logo is a computer programming language used for functional programming. It is an easier-to-read adaptation and dialect of the Lisp language; some have called it Lisp without the parentheses. Today, Logo is known mainly for its turtle graphics, but it also has significant facilities for handling lists, files, I/O, and recursion. Logo was created for educational use, more so for constructivist teaching, by Daniel G. Bobrow, Wally Feurzeig and Seymour Papert. It can be used to teach most computer science concepts, as UC Berkeley Lecturer Brian Harvey does in his Computer Science Logo Style trilogy. HistoryLogo was created in 1967 at Bolt, Beranek and Newman (BBN), a Cambridge, Massachusetts research firm, by Wally Feurzeig 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 an SDS 950. The goal was to create a math land where kids 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. The first working turtle robot was created at MIT 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. Later, BBN 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. DesignLogo's best-known feature is the turtle, which is an on-screen cursor (derived originally from a robot of the same name), which can be given movement and drawing instructions, and is used to programmatically produce line graphics. It is traditionally and most often represented pictorially either as a triangle or a turtle icon (though it can be represented by any icon). Turtle graphics were added to the Logo language by Seymour Papert in the late 1960s to support Papert's version of the turtle robot, a simple robot controlled from the user's workstation that is designed to carry out the drawing functions assigned to it using a small retractable pen set into or attached to the robot's body. As a practical matter, the use of turtle geometry instead of a more traditional model mimics the actual movement logic of the turtle robot. Turtle geometry works somewhat differently from (x,y) addressed Cartesian geometry, rather operating in a Euclidean space (i.e., relative measures and angles without an origin, unlike coordinate-addressed systems such as PostScript). The turtle moves with commands that are relative to its own position, LEFT 90 meant rotate left by 90 degrees. A student could understand (and predict and reason about) the turtle's motion by imagining what they would do if they were the turtle. Papert called this body-syntonic reasoning. Some Logo implementations, particularly those that allow the use of concurrency and multiple turtles, support collision detection and allow the user to redefine the appearance of the turtle cursor, essentially allowing the Logo turtles to function as sprites. Turtle geometry is also sometimes used in environments other than Logo as an alternative to a strictly coordinate-addressed graphics system. For instance, the idea of turtle graphics is also useful in Lindenmayer system for generating fractals. Logo is generally known as an interpreted language, although recently there have been developed compiled Logo dialects - such as Lhogho or Liogo. Logo is not case-sensitive but retains the case used for formatting. It is a compromise between a sequential programming language with block structures, and a functional programming language. There is no standard LOGO, but UCBLogo is highly regarded. It is a teaching language but its list handling facilities make it remarkably useful for producing useful scripts. Article source: http://en.wikipedia.org/wiki/Logo_programming_language Go back to Programming Articles home page
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