Event Driven Programming Event Driven Programming Key Features Event Driven Programs

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					Event Driven Programming
               Key Features
Event Driven Programs

Typically used for most modern day
 software applications examples include:
 word processing, spreadsheets, drawing
 packages etc.

Usually used for GUIs where many types
 of events are generated i.e. clicking on a
 button or another object
Key features
 Event Handlers
 Trigger Functions
 Events
 Event Loops
 Forms
 Flexibility
 Service oriented
 Suitability for GUIs
 Simplicity of programming
 Time Driven
Event Handlers

VB.Net uses subroutines for event
 handling, with the name of the object
 followed by the name of the event – see
 below:               Event

Trigger functions
 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 Loops
 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
Service Oriented
 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
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
 the tasks.

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