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142 Masterpiece 3 • The LEGO Turning Machine

Programming the Machine

In this section, we will see how we can actually give “intelligence” to our Turing
Machine. We will take the first example shown in this chapter.That is, making a machine
that adds two integers and translates them into NQC code.

NOTE

The program for the operation of the LEGO Turing Machine can be found on the
CD-ROM that accompanies this book.

We will follow good programming practice and split the programming into separate
procedures. We will examine them one by one.There are multiple procedures, identified
by the keyword void, meaning that they don’t return any value, and a main program called
task main().
First, we should define two variables:

■ One to store the current state the machine is in, indicated by a number

■ The other used by the program to tell when it has finished its job and should
stop (I choose to name it “done” because “stop” is a reserved keyword in NQC).

In NQC there are no Boolean variables to handle a True/False value, so the latter also
should be declared as int. Both are initialized to zero.
int state = 0;
int done = 0;

Some setup must be done to tell the RCX that we will be using two sensors: a touch
sensor for the step-by-step movements, and a light sensor to read the symbol inside the
cell. Here we set motor’s power to the maximum, and finally take advantage of a new fea-
ture of the RIS 2.0 firmware (version 0328) and set the RCX’s LCD display to always