Variables and Sub-Functions in the NQC Language

We discussed variables and sub-functions previously here.

Now let's discuss how to use them in the NQC language (and most other textual programming languages like C,Java, Python)

Variables in NQC

Remember, a variable is a symbolic name for a memory cell.

With NQC, a programmer must declare a variable, then s/he can put values into the variable or get values out, e.g.,

task main ()
{

int greens; // declare the variable 'greens' as an integer (whole number)
greens=0; // assigns the value 0 to the variable 'greens'
if (greens==0) // check the value of 'greens' and compare it to 0
{

// ... do something

The declaration statement names some memory cell:

greens -----> 1000

The assignment statement puts a value in that memory cell:

You must always declare a variable for assigning to it, and you should always assign to it before checking it.

Question 1: How would you add one to the previous value of 'greens'?

Question 2: How would you use a variable to do something n times?

Sub-Functions in NQC

Sub-Functions allow us to break a program into small, understandable parts, to give a name to a sequence of commands.

In Lego block diagram programming, we created a sub-function with the "My Blocks" facility.

A sub-functions is called a sub in NQC, e.g.,

task main()
{

// ...do some stuff
spinAround(); // this calls the subfunction
// ...do whatever else

}
sub spinAround() {

OnFwd(OUT_A);
OnRev(OUT_C);
Wait (50);
OnFwd(OUT_A+OUT_C);

}

Note that you call a sub-function by referring to its name (see call in main).

In-Class Task:

Write a program with a main task and two sub-functions, spinAround and playMusic (just have it play some sounds). The main function should call the subfunctions three times, using a while loop. You'll need to define a variable for the loop counter.