Copyright Don Sleeth, 1998

Page 2 - Let's Get Started

Where are we headed?

For our first project we will be to develop a few procedures to add variety to the turtles movement. We will put them together in a small test program. Learning these techniques will enable you to make your own interesting scenes with lots of movement and animation.

What is a program?

A program is a list of instructions to the computer. Computers were designed to carry out instructions, pretty much one at a time. Let's give our computer some instructions. Start up MicroWorlds, if you haven't already. Here is what you should see:

Lets do some experiments to find out just what is an "instruction". We will start off with a suggested definition but we will find that we need to make some changes to it as we learn. We need some place to start, so I just want to tell you that all the words that are built-in to MicroWorlds are called "Procedures".

Definition of an "Instruction", Version 1:

An instruction, in the Logo language, is the name of a procedure

Test of Version 1
In the command center, type forward and press Enter.

Test Result
forward needs more inputs

So we need to modify our definition of an instruction.

Definition of an "Instruction", Version 2:

An instruction, in the Logo language, is the name of a procedure followed by its required inputs.

Test of Version 2
In the command center, type forward 10 and press Enter.

Test Result
Success, the turtle moved forward.

Another Test of Version 2
In the command center, type forward 10 wait 1 back 5 and press Enter.

Test Result
Success, the turtle moved forward, then back.

But this is more than just one procedure as our current definition states. So, again, we need to modify our definition of an instruction.

Definition of an "Instruction", Version 3:

An instruction, in the Logo language, is the name of a procedure followed by its required inputs or a list of procedures each with their required inputs.

Let's leave that as our current understanding of what an instruction is. We will find out later that there is a little more to it, but we will fix it then.

So, if a program is a list of instructions to the computer and an instruction is a list of procedures and MicroWorlds already knows piles of procedures, we must be ready to write a program!

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