Event Driven Programming
Event Driven Programs
Typically used for most modern day
software applications examples include:
word processing, spreadsheets, drawing
Usually used for GUIs where many types
of events are generated i.e. clicking on a
button or another object
Suitability for GUIs
Simplicity of programming
VB.Net uses subroutines for event
handling, with the name of the object
followed by the name of the event – see
These are used along with the object’s name to determine with event handler to run
Every object has a range of trigger functions, one for each possible event that can
happen to it. For example, txtText could have an event handler for the following
triggers: GotFocus, TextChanged etc...
Temporal triggers mean triggers set off by duration of time
State triggers are when the current situation causes a certain set of procedures to run
What is the trigger here??
Event Driven Programs have event loops built into the
environment. The loops keep testing the interface to
detect whether anything has happened, such as clicking
on a button or typing into a textbox etc.
Event Loops are also known as event listeners
Programmers have enormous control over
where to place code and how to start it.
Every object has a good choice of events
that a program can respond to. These
events give an excellent level of control
over exactly what the program will respond
to when the user does something
A lot of networked applications use service oriented
techniques so that different applications can reuse code
Service oriented applications separate the service
implementation from the program interface that uses the
An example is a request from a database.
XML (Extensible Markup Language) is commonly used
for interfacing with such service oriented architectures.
Time driven programming is often used in
real time, where code execution is
controlled by the computer clock.
A program is divided into a set of tasks
that need to be regularly activated. The
activation pattern us stored into a dispatch
table, where rules are used to schedule