programming-for-dummies

36
Planning Ahead with Structured Programming
One of these smaller tasks might be, “Identify the lottery numbers that tend to
appear often.” A second task might be, “Pick the six numbers that have appeared
most often and display those as the potential future winning numbers.”
The idea is that writing a large program may be tough, but writing a small program
is easy. So if you keep dividing the tasks of your program into smaller
and smaller parts, eventually you can write a small, simple program that can
solve that task. Then you can paste these small programs together like building
blocks, and you’ll have a well-organized big program — theoretically.
Now if you need to modify part of the large program, just find the small program
that needs changing, modify it, and plug it back into the larger program,
and you’ve just updated the larger program.
Ideally, each small program should be small enough to fit on a single sheet of
paper. This makes each small program easy to read, understand, and modify.
When you divide a large program into smaller programs, each small program
is a subprogram.
If you divide a program into multiple subprograms, you have two options for
where to store your subprograms:
✦ Store all of your subprograms in a single file.
This option is fine for small programs, but after you start dividing a program
into multiple subprograms, trying to cram all of your subprograms
into a single file is like trying to cram your entire wardrobe of shirts, pants,
and underwear into your sock drawer. It’s possible, but it makes finding
anything later that much more difficult.
✦ Store subprograms in separate files, as shown in Figure 2-4.
Main Program
Main Program
Subprogram #1
Figure 2-4:
You can
store
subprograms
in one big
file or in
separate
files.
Subprogram #2
Subprogram #3
Subprogram #4
A single file can hold the
main program plus all of
its subprograms.
Subprogram #1
Subprogram #2
Subprogram #3
Subprogram #4
You can store the main
program and all of its
subprograms in separate
files.