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Thomas von Fintel, Glen Pate

LOGO Frequently asked Questions (FAQ)

Extracts from: cher.media.mit.edu/pub/logo/comp.lang.logo.
( Edited for WWW by Glen Pate, Dec95, Feb96 )


1a: What is Logo?
1b: BASIC is interactive and interpreted.
Why not program in BASIC?
2: What was the genesis of Logo?
3: What is turtle geometry?
6: Where can I learn more about Logo?
9: Public Domain and Shareware Logos?
13: What does Piaget have to do with Logo?
23: Books
23a: Using LOGO to learn other stuff (Mostly Math)

1a: What is Logo?

Logo is a computer programming language designed for use by learners, including children. One of the ideas guiding its creation was the principle "low floor, high ceiling." This means that it should be easy for the novice programmer to get started (the "low floor") writing programs and getting satisfaction doing so, but that the language should be powerful and extensive in a "sky is the limit" sort of way (the "high ceiling").

Logo was originally developed by Daniel Bobrow and Wallace Feurzeig at Bolt, Beranek and Newman, Inc., and Seymour Papert, at the Massachusetts Institute of Technology in the 1960's. (See "2: What was the genesis of Logo?" below.) It was based on the goal of allowing people to use computers to manipulate things more familiar than the then-prevalent numbers and equations. Logo borrowed the techniques of symbolic computation (manipulating words and ideas) from the LISP programming language used in artificial intelligence research. Powerful computer science concepts of the procedure, recursion, programs-as-data are built into Logo.

In its early days Logo was used to control a simple robot called the "turtle" because the first one had a turtle-like shell. Children would type commands such as FORWARD 50 to make the robot go forward 50 steps, or RIGHT 90 to make it turn right ninety degrees. The turtle robot carried a pen, so children could make drawings on a piece of paper.

Later the turtle "migrated" to the computer screen when graphics terminals became available. ....

Logo's designers came to see the turtle as an important part of the Logo language. Children (and later teachers) who were first using computer could begin by "talking to the turtle," typing in commands to make it move. They could imagine how the turtle moved by "playing turtle"---moving their bodies as the turtle would. Papert called this "body syntonicity," the idea of understanding how some external object worked by thinking about your own body. He felt that the turtle as an "object to think with" was a powerful way to be introduced to the idea of programming.

Logo teaches problem solving, logical thinking, constructive methods and allows the user to interactively create and manipulate mathematical processes.

[Fred Martin | fredm@media-lab.media.mit.edu | (617) 253-7143 MIT Media Lab | Epistemology and Learning Group | Cambridge, MA 02139]

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1b: BASIC is interactive and interpreted.
Why not program in BASIC?

In the beginning all BASIC variables were global and all BASIC control was based on line numbers. BASIC provided terrible support for composing hierarchical programs, and hierarchy is the primary tool for partitioning software complexity and making programming problems tractable. Logo, on the other hand, treats all programming uniformly as the creation and invocation of functions composed, in their turns, of functions, down to the core functional vocabulary of the language. New versions of BASIC have borrowed some functional features from other programming languages, putting them into non-standard forms that are not portable among BASIC dialects. Logo, in contrast, has had composition of functions at its core from the beginning, and is close enough to a standard to support code and design sharing among all well-conceived dialects. Logo's lists and property-value pairs support data structuring superior to any standard BASIC facilities. Logo also continues to support run-time equivalence of language and data, a characteristic common to LISPs but not to most other programming notations. This feature gives very strong support for the ability to create custom languages tailored to their applications.

[Dale Parson, Bell Labs, dale@mhcnet.att.com]

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2: What was the genesis of Logo?

According to Wally Feurzeig in his article in *Digital Deli*, 1984, Logo was named by him at BBN and Paul Wexelblat built the first turtle on the floor. The name of the article is Logo Lineage. In the article Seymour Papert was called in as a consultant on the functional characteristcs.

[Linc, James Internet: Gowj@novavax.nova.edu]

Logo was developed at BBN in the 60's, Seymour was a consultant on the BBN project. The first implementation of what we now know and love as Logo, was written in LISP (surprise, huh?) on a PDP-1 (at BBN). Its name was "ghost".

The goal then, was basic problem solving; the turtle gave immediate (non-written) feedback so bugs could be spotted *and it was fun*. Lots of other effects have been proposed as causes... Power was NOT a significant factor in the design, ease of use for non-typists who had to use a Teletype (r), was a big consideration, plus informative error comments.

The turtle was a rather late innovation, Logo is not too much different now from the basic concepts before I built the first turtle. The first turtle was a radio controlled (wireless) floor roamer named "Irving" -- after the punchline of a then current joke. Irving had touch sensors and could do forward, back, right, left (rotations), and ding (Irving had a bell). Irving had his name changed when I started dating a girl who's father was named Irving. I designed and built Irving, and I added the turtle commands to Logo (then implemented on a different BBN PDP-1 in Assembly Language).

Folklore: Earliest school users... Muzzy Jr High, Lexington MA the elementary school in Lincoln, MA FROTZ, GEFULTE, UNFROTZ and KREBS were 4 early built-in function names (hidden and unlikely to be guessed).

Both Wally F. and I are available via email (Wally is feurzeig@bbn.com, and I am wex@uml.edu) although I am not able to do the FAQ, I would certainly be interested in helping with the history of the early Logo. BTW, Seymour is seymour@media.mit.edu (MIT Media Lab, down the road a piece).

[Paul Wexelblat, University of Massachusetts Lowell, wex@cs.uml.edu]

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3: What is turtle geometry?

Turtle geometry is geometry that describes paths "from within" rather than "from outside" or "from above." For example, "turn right" means turn right relative to whatever direction you were heading before; by contrast, "turn east" specifies an apparently absolute direction. A Logo user or program manipulates the graphical turtle by telling it to move forward or back some number of steps, or by telling it to turn left or right some number of degrees. There are two advantages to turtle geometry. One is that many paths are more simply described in relative than in absolute terms. For example, it's easy to indicate the absolute coordinates of the corners of a square with vertical and horizontal sides, but it's not so easy to find the corners of an inclined square. In turtle geometry the same commands (go FORWARD, turn RIGHT 90 degrees, etc.) work for squares with any orientation. The second advantage is pedagogic rather than computational: turtle geometry is compatible with a learner's own experience of moving in the world--it's "body syntonic."

[Brian Harvey, bh@anarres.cs.berkeley.edu]

With its graphical pen down a turtle draws colored lines as it moves. A remarkable array of graphical creations, from elementary shapes such as circles and squares to complex recursive curves and fractal monsters, can arise from this body-centered model of geometry. Logo does provide for Cartesian coordinate and global heading usage as adjuncts to the body-centered turtle commands.

The first turtles were mechanical devices that carried pens and drew on paper on the floor. Modern Logos support at least one graphical turtle and multiple graphical colors, sometimes of varying line widths. Turtle graphics now also appear in other programming languages, sometimes as function or class libraries. Advanced turtle graphics packages provide for multiple concurrently acting turtles with velocity.

For introducing young kids to turtle geometry I advocate going for walks with good local maps in hand. In fact the best maps are those for beginning orienteering courses. Orienteering is a sport where you look for checkpoints in the woods using a detailed topographical map. Beginners' courses are mostly along trails and other "linear features," and compasses are useful mostly to figure which way to orient the map when you first get started or when you lose focus (especially kids). Advanced courses can require more serious compass use. The left and right turns, scaled steps, planning, problem solving, even the geometry, linear algebra and fractals are there if you care to pursue them. I understand from a pilot friend that navigating from the air is just as good, as undoubtedly is navigating at sea, but at about $3 to $5 per map at a typical meet you can't beat orienteering as a cost effective way for introducing kids to navigation and all the math that follows. In the U.S. to find your local club contact:

U.S. Orienteering Federation
P. O. Box 1444
Forest Park, GA 30051

Beginners' courses are < 2 miles, take snacks for the kids.

[Dale Parson, Bell Labs, dale@mhcnet.att.com]

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6: Where can I learn more about Logo?

a. *Mindstorms: Children, Computers and Powerful Ideas*, Seymour Papert, Basic Books, 1980.

b. *The Children's Machine: Rethinking School in the Age of the Computer*, Seymour Papert, Basic Books, 1993.

c. The Epistemology and Learning Group at the MIT Media Laboratory, headed by Seymour Papert, 20 Ames Street Room 309, Cambridge, MA 02139. Write to E&L; Publications and ask for the publications bibliography, or send a request to "el-pub@media.mit.edu".

Some papers are available via anonymous FTP from cher.media.mit.edu ( (Postscript printer required).

d. The Logo Foundation, 250 West 57th Street, New York, NY, 10107-2603, Michael Tempel, president. michaelt@media.mit.edu or phone 212 765-4918, fax 212-765-4789. They publish *Logo Update* three times a year for free, also distribute Logo books, articles, videos and software.

e. The International Society for Technology in Education (ISTE), 1787 Agate Street, Eugene, OR 97403-1923, phone 503-346-4414, publishes *Logo Exchange*, a quarterly journal, and a dozen Logo books. ISTE also supports SIGLogo, a special interest group for Logo-using educators.

f. Council for Logo in Mathematics Education (CLIME), 10 Bogert Ave., White Plains, NY 10606, phone 914-946-5143, an affiliate of the National Council of Teachers of Mathematics, publishes a newsletter and CLIME Microworlds--collections of Logo programs and tools.

See Books below.

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9: Public Domain and Shareware Logos?

a. Berkeley Logo (this last updated August, 1993):

Release 3.0 of Berkeley Logo is now available by anonymous FTP. Versions are available for Unix systems, DOS machines, and Macintoys.

The PC distribution includes two executable programs. BL.EXE runs on any PC, but is limited to 640K of memory. UCBLOGO.EXE requires a 286-or-better processor, but is able to take advantage of extended memory if you have it. Read the README file for technical details.

Thanks to many people who reported bugs, and several people who actually sent bug fixes. I am particularly grateful to George Mills, who caught a bunch of bugs, and to Randy Sargent, who finally zapped the dreaded memory leak.

FTP to anarres.cs.berkeley.edu and get any of the following files:

pub/ucblogo/ucblogo.tar.Z Unix sources and documentation pub/ucblogo/blogo.exe PC version, PKZIP form, including executables BL.EXE and UCBLOGO.EXE pub/ucblogo/ucblogo.sea Mac version, StuffIt form, w/ executable Logo pub/ucblogo/usermanual Just the documentation file. pub/ucblogo/csls.tar.Z Logo programs from Computer Science Logo Style

Be sure to use BINARY transfer mode when retrieving the archive files!

The DOS version is in the form of a self-extracting PKZIP archive. To install it, put blogo.exe on your hard disk and say blogo -d

The Mac version is in the form of a self-extracting StuffIt archive. To install it, just copy to your hard disk and double-click on it.

The Unix version is a compressed tar file. To install it, copy to your directory, then say uncompress ucblogo.tar tar -xf ucblogo.tar

The DOS and Mac versions include a SOURCE subdirectory containing the C source files used to compile Berkeley Logo. If you don't want to play with the code, you can delete this directory and all its contents.

Advantages of Berkeley Logo:

* It's free.

* It comes with source files (in C).

* Logo programs are completely compatible among Unix, PC, and Mac.

Disadvantages of Berkeley Logo:

* It's pretty slow.

* It doesn't do anything fancy about graphics. (One turtle.)


[Brian Harvey, bh@anarres.cs.berkeley.edu]

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13: What does Piaget have to do with Logo?

Seymour Papert's early work with AI caused him to think about what human intelligence is, which eventually led him to Geneva where he studied with Piaget from 1958 to 1963. The strong influence of Piaget's ideas on Papert's thinking is evident in the indexes of his two important books. Mindstorms lists about 20 Piagetian references and The Children's Machine about 24. No other references to persons in either book even comes close (most are four or less).

Without diminishing the unique contribution of Papert's original thinking and application, it must be said that Piaget's ideas are such an integral part of Papert, that virtually everything about Logo has something to do with Piaget. One example will be my contribution:

Piaget described stages of mental maturation through which children go with age and experience. Each stage is characterized by a type of thought that is subsumed and transcended by the subsequent stage. The stage of concrete operational thought, where most elementary and middle school children function, is characterized by thought that is logical when concretely embodied. In other words, children of about eight to 14 years old can usually functional logically when the problem is of a type that can be worked out with objects. Thinking about thinking, or metacognition, was believed to be a formal operational process, too abstract for concrete stage thinkers. Papert asserts that by providing the Turtle as an object to think with, Logo furnishes for ideas previously known only through abstraction, a concrete embodiment. Logo thus allows the learner to externalize his or her expectations or intuitive notions into the concrete form of a program, where the notions are accessible to reflection.

[Linda Jones <lijones@eis.calstate.edu>]

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23: Books

Logo philosophy:

Papert, Seymour: *Mindstorms* (Basic Books, 1980). [auch deutsch]

Papert, Seymour: *The Children's Machine* (Basic Books, 1993). [auch deutsch]

For late elementary through junior high kids:

Abelson, Harold: *Apple Logo* (McGraw-Hill) [auch deutsch]

For high school to adult:

Harvey, Brian: *Computer Science Logo Style* (MIT Press) vol. 1: Intermediate Programming vol. 2: Projects, Styles, and Techniques vol. 3: Advanced Topics

Friendly, Michael: *Advanced Logo* (Lawrence Erlbaum Associates)

Boecker, H.-D., H. Eden, G. Fischer: *Interactive Problem Solving using LOGO*, (Lawrence Erlbaum Associates, 1991, ISBN 0-8058-0305-X (cloth) / 0-8058-0306-8 (paper))

Burke, Michael, and L. Roland Genise: *Logo and Models of Computation* (Addison-Wesley)

A shareware tutorial:

I have written a book specifically for teachers and teachers-in- training called ALL ABOUT LOGO. It's available as shareware. I have used many of the ideas in Brian's (see above) excellent book, and included the traditional graphics material. The format is also more "traditional" in that it includes suggested "Explorations" at the end of each of the 14 chapters. Version 1.1 (geared for Macintosh LogoWriter) is available by ftp from cher.media.mit.edu /pub/logo. I have written an update to this (version 1.2) and am working on version 1.3 which removes the last (I hope!) of the technical errors. Version 2.2 (geared for Apple II LogoWriter) is also available. I plan to replace Version 1.1 with version 1.3 and add version 2.3 to the ftp server in the next couple of weeks. I'd be pleased to send a hard copy version for your inspection if you like.

[Dave Kressen dkresse@ctp.org]

Using Logo to learn other stuff (mostly math)

Abelson, Harold & Andrea diSessa, *Turtle Geometry* (MIT Press) The classic text on the subject.

Cuoco, Albert: *Investigations in Algebra* (MIT Press)

Clayson, James: *Visual Modeling with Logo* (MIT Press)

Goldenberg, E. Paul, and Wallace Feurzeig: *Exploring Language with Logo* (MIT Press)

Hoyles, Celia, and Richard Noss, *Learning Mathematics and Logo* A collection of research papers about various aspects of the use of Logo in math classrooms.

Lewis, Philip: *Approaching Precalculus Mathematics Discretely* (MIT Press)

Prusinkiewicz, Przemyslaw & Aristid Lindenmayer, *The Algorithmic Beauty of Plants* (Springer-Verlag, 1990). Plant growth/structure modeling based on turtle geometry and L-systems, excellent illustrations.

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Updated 28 Aug 97: Pate@erzwiss.uni-hamburg.de, glenpate@acm.org

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