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try it out 4-2
What do you think will happen if you set the initial direction to 0° (up) instead of
90° (right)? Will the script work? If not, how could you fix it? Make this change
and run the script to test your answer .

working with Procedures

Now that you know why it’s important to break your program down into
smaller parts and tackle them one at a time, let’s discuss how to perform
this division. Every problem is different, and there is no “one size fits all”
solution—but that’s what makes this a fun puzzle!
In this section, we’ll first explore the top-down process of dividing a large
program into modular pieces with a clear logical structure. We’ll then dis-
cuss another way of building complex programs: the bottom-up process of
combining existing procedures. Figure 4-23 shows a high-level view of these
two approaches.

Start Top-Down End Bottom-Up
Process Process

End Start

Figure 4-23: Illustrating top-down (left) and bottom-up (right) approaches

In both diagrams, the problem we want to solve is at the top, and the
individual steps that build our solution are at the bottom. You can start
from whichever level makes sense to you.

Breaking Programs Down into Procedures
The first step in solving any programming problem is to fully understand
the problem. After that, you can plan a general solution and divide it into
major tasks. There is no right or wrong way to go about dividing up any par-
ticular program, and with experience, you will get better at deciding what
“major” means. Working from the general solution down to its specifics
ensures that, at least, the overall logic of the program is correct.
House .sb2 To demonstrate this problem-solving strategy, let’s consider how we
would draw a house similar to that shown in Figure 4-24.

84 Chapter 4
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