Logo

Reviewed by Anne Ramkaran

 

 

Issue 17

Sep/Oct 85

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Reviewing a language is rather difficult as, to some extent, whether you like it or hate it depends on what you want to do with it. As I use Atari computers in a school, I was particularly interested in the educational uses of Logo.

The Atari version of Logo is written by Logo Computer Systems of Montreal and is a full implementation, not just turtle graphics. It comes in the usual, somewhat extravagant, Atari packaging as a cartridge and two manuals. The manuals are much better than usual and are very useful so that it is possible to get on reasonably well without buying extra books. Some of the sample programs in the reference manual are actually useful! One of the manuals is a 153 page introduction to Turtle graphics and the other is a 209 page reference manual.

WHAT DOES LOGO DO?

Logo allows the user to define procedures and once defined these stay in memory (unless erased) so they can be used repeatedly. Recursion is allowed so a procedure can call itself. Procedures reside in an area of memory called 'workspace' and the entire contents of the workspace can be saved on disk or tape.

One of the best features of Logo is, of course, Turtle graphics. The Atari version offers four turtles which can move independently and have separate speed control. Commands to move are easy as are turning commands. Error messages are beautifully explicit. For example "I don't know how to". A pleasant change from the error numbers given by Atari Basic.

The Atari version differs from many others in allowing collision detection. This is easily available by setting up 'WHEN DEMONS'. Once the demons are enabled they remain active until cleared. This example shows how easy it is to set up collision detection:

WHEN 19 [INSTRUCTION LIST]

When Turtles 0 and 1 collide (event 19) the specified instruction list or procedure is executed. Position of the joysticks and use of the fire button can also be detected.

It is a pity, given the graphics capabilities of the hardware, that there is no choice of graphics mode available. The lines drawn by the Turtles are relatively low resolution which limits some possible applications. A shape editor is provided allowing up to 16 different shapes to be designed and held in memory. The shape of the Turtle can be changed to any one of these very rapidly, allowing simple animation.

As well as supporting Turtle graphics, Logo also provides useful list processing and has abilities for file handling. This might well be of interest to those who find the lack of proper string arrays in Atari Basic a handicap, however, as with all interpreted languages, this type of program runs slowly and offers few advantages over something like Microsoft Basic II. If you need fast list processing and string handling, look for a language which is written for the purpose.

EASY TO START

At entry level (Turtle graphics) Logo is easy to understand. A six year old can get the Turtle moving and draw on the screen. At a more advanced level the language, as might be expected, becomes more difficult and is no easier than Basic.

From an educational point of view Logo is interesting to work with. It undoubtedly helps children to learn about problem solving. The big advantage over structured Basic is that the graphics are easy, children like to draw things on the screen and are therefore better motivated. As relatively few commands are needed to get started it is easy enough for young children to use. The Turtle graphics are excellent for investigating simple geometry. It is probably best used with groups of children by explaining the commands available then allowing the children to work out their own procedures to solve problems which as far as possible they choose themselves. In this way the children learn from their own experience.

I would recommend Logo to anyone using the Atari computers in education and also suggest it to parents who bought the computer in the hope that their children would learn more than how to zap aliens!!

Logo should be available from local suppliers at approximately 60. Educational users should be able to get a discount if they contact Atari at Slough.

Anne Ramkaran is a teacher in Liverpool. She has a set of programs developed for the school for creating text files in Greek. These are on disk and can be printed to a 1020 printer when required. Anne is happy to supply the package to anyone interested free of charge if they send a blank disk plus return postage to her at 318, Aigburth Road, Liverpool, L17 6AA.

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