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functions

Don't duplicate your code...

When you need to add a new feature to a program that’s similar to some
other code in the program, you might be tempted to just copy and paste
the code. You'll find that code bloat is
common in lots of programs,
In practice, that’s actually a pretty bad idea, because it can lead to code even code written by
bloat. Code bloat means that you have more code in your program than professional programmers.
you actually need. Your programs will get longer, and they’ll get a lot
harder to maintain.

Here‛s the printout of the tic-tac-toe
game. If you really want me to change the
colors of the crosses, I‛ll just need to replace
the code that displays each of the 9 squares. That‛s
the same code in 9 different places. Oh, and if you
want me to change the 0s...

...Reuse your code instead

Programming languages all come with features that allow you to reuse
code. So what’s the difference between copying and reusing code?

If you copy code, you simply duplicate it. But when you reuse code, you
have a single copy of the code that you can call in all the places that
you need it. Not only will your programs be shorter, but it also means that
when you amend code, you will need to change it only once and in one
place only.

So you want a new gravity-bomb
launcher added to each of the
star-fighters? No problem. I‛ll change
a few lines of code and every craft in
the fleet will be updated.

So code reuse is a good thing. But how do you do it?

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