Hardware Reference
In-Depth Information
British Broadcasting Corporation, BBC for short, even went as far as to create
its own computer for schools to accompany a television series on computer
programming. It was a huge success and was just one of many projects. One of
these projects was the Logo programming language.
Most programming languages are mathematical: the acquisition, modii ca-
tion, and use of numbers. Logo was different; it was based on logic. (Hence the
name Logo is derived from the Greek word
logos
, thought.) Although designed
for several reasons, an entire generation remembers it for the famous turtle.
The turtle was represented as a computer rendered triangle on our large
cathode-ray tubes connected to primitive computers. The turtle was free to
roam across the screen but needed instructions. For some unknown reason, it
had a paintbrush strapped onto its tail. It could be told to put the brush down
(to start drawing) or to pick it up (to stop drawing). It then required the user
to give it instructions. Anyone who has used BASIC probably knows about the
i rst program anyone writes:
10 PRINT "Hello, world!"
20 GOTO 10
This would print out endless lines of text and was a good visual start to pro-
gramming but did not go any further. The turtle, however, was different. For
example, take this program:
FD 100
RT 90
FD 100
RT 90
FD 100
ERT 90
FD 100
FD is short for forward. The turtle is instructed to advance for 100 “units”
and then make a right turn (RT) by 90 degrees. Then it is instructed to advance
another 100 units and so on. The result? A square as shown in Figure 22-1.
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