programming-for-dummies

Organizing a Program with Object-Oriented Programming 43
The user can do dozens of different possible events, but the most common
events are clicking the mouse or moving the mouse pointer over an item.
Event handlers typically do one of three things:
Book I
Chapter 2
✦ Identify what the user did, such as click a button
✦ Retrieve information from the user interface, such as when the user
types something in a text box
✦ Display information to the user, such as displaying an error message
After you’ve written one or more event handlers for your user interface, you
have a complete working user interface. Now you just have to attach this
user interface to a working program.
Different Methods
for Writing
Programs
Writing your program
Some people write their program first and then design a user interface
around it. Other people design their user interface first and then write their
program to work with it. The whole point of event-driven programming is to
separate your program from your user interface so you can focus on making
each part work individually.
Event-driven programming focuses mostly on designing a user interface and
making it work, but does little to help you write your actual program. To
write your program, you can use structured programming or object-oriented
programming (or both, or neither).
After you’ve written your program, you “attach” the program to your user
interface by writing event handlers. Event handlers “glue” your user interface
to your actual program. With event-driven programming, you can be
pretty sure that your user interface will always work perfectly. You just have
to worry about errors in your main program.
Organizing a Program with Object-Oriented
Programming
Structured programming helps you organize and divide your program into
smaller, more manageable pieces. For small- to medium-sized programs,
dividing a program into smaller programs is fine, but the larger your program
gets, the more smaller programs you’ll have to worry about. Eventually, computer
scientists discovered that they needed another technique for dividing
large programs into parts, so they called this new technique object-oriented
programming (often abbreviated as OOP).