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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