Computers are used to control many types of devices such as robots. The computers controlling the robots must be programmed with instructions to tell them what to do. The programs [program: a list of instructions written in a programming language ] are written in computer languages. Logo is one such language.
Logo is a simple computer programming language which can be used to control devices. For example, a small robot known as a turtle [turtle: a robot that can be programmed using the programming language Logo to carry out simple commands, eg forward and backward ] can be moved around the floor using logo. Logo is often used with a screen turtle, which is an object on the screen used to simulate how a turtle moves around the floor. There are many commands [command: a directive given to a computer program ] which can be used to control the turtle.
Here are some examples of the most common Logo commands:
|FORWARD 50||move forward 50 steps|
|BACK 50||move backward 50 steps|
|LEFT 90||turn 90° left|
|RIGHT 90||turn 90° right|
|PENDOWN||lower pen and begin drawing|
|PENUP||raise pen and cease drawing|
These commands can be used to draw a square on the screen:
The same commands can be written more quickly using the REPEAT command, for example:
REPEAT 4 [FORWARD 100 LEFT 90]
This single command would have the same effect as the eight individual commands above - it draws a square.
The REPEAT command can be used to create any number of patterns. For example, a shape similar to a spirograph was created with this command:
REPEAT 30 [FORWARD 100 RIGHT 156]
Storing a series of commands like this creates a simple program. The order of the commands in a program is vital. If it is in the wrong order, the program will not work as expected.
Computer programming languages are very fussy. Any errors, however small, will cause the program not to work. The computer won't like spelling mistakes or, for example, if you forget to put a space between FORWARD and 50.
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