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Copy of Copy of Key Features of Event Driven Programming

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david messent

on 4 March 2013

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Transcript of Copy of Copy of Key Features of Event Driven Programming

Event Driven Programming Service Oriented Event Driven Programming What it it? Time Oriented Event
Driven Programming What is it? Event Handlers Trigger Functions What is it? - It is when the user writes a
specific code that will run on
a given event. Example - An email notification is
an event that happens due
to a code running to alert
the user, by vibrating/flashing
(mobile) or creating a pop up
(computer). What can it do? - Can run several services at
the same time. - It is when the user
writes a specific code
that will run at a set
time. Example - Scanning for a virus.
You could set it to
scan every second, or
every hour or every
week. This is often known as 'Timer' Trigger. What is it? - It is the actual code
which is run when a
trigger occurs. - If the user clicks
on a button, it
would trigger the
event handler for
Button Click, which
will run the code. Example By Adèle Hanks - 12038710 - It is used to select which
event handler to run
according to which event
occurred. Events What is it? - There are many possible
events that can trigger
the event handlers to
run. Mouse Events - Examples Event Loops What is it? Example - Clicking on a button
or typing into a
text box. - If an event is detected,
event is passed to the
trigger functions, which
then call the appropriate
event handler to run any
code in the program
that was designed and
written for the event. Forms What is it? - Are major features of
most event driven
environments, as they
are what the user sees
when the program runs. Example 1 Load:
- an event that occurs
when a form is first used. Activated:
- an event that occurs
every time the form
receives the focus. Simplicity of Programming - Program Development can be easy
with an event driven language. Ease of Development - The mouse events
include left click,
double left click,
right click, and
hover. Keyboard - The keyboard events
include key press,
key down and key up. HTML - The HTML object
events include clicking
on an object which might
then connect connect to
a linked web page. Forms - Form Events include
the load event when
the form appears
for the first time. User Interface - User Interface events
include anything that
the user does with a
GUI operating system
or to the form of a
running program. Example 2 - EDP languages can make programming
very simple, as the
programming language is very visual. - A control such as a button
can easily be put on to a
form from the toolbox. - Many event driven languages make
coding simpler by having detached
menus for possible commands. - These make programming much
easier as they:
- show the programmer the choice of
commands for that part of the code
- allow the programmer to choose the
appropriate command without
actually typing it.
--> quicker and more accurate. - Visual components
automatically add code. Example - Event driven language will
run with as little as only the
code for a simple event to be
completed. - Testing is easier because
each event can be tested
in turn. Operating Systems How can an operating system can be viewed as an event driven application? Example - Operating systems for personal
computers have always been
event driven.
- When DOS (Disk Operating
System) was still being used,
the operating system was event
driven to respond to interrupts
from peripherals (e.g. printer)
to the processor.
- Modern operating systems have
to deal with all the events that
previous systems had as well as
all the modern events such as:
- mouse when a button is clicked
- when a touch screen is touched These are events that peripherals sent
to the operating system for handling:

- keyboard when a key is pressed.
- keyboard when Ctrl + Alt + Del are
- printer when it whats data for the
next page.
- printer when it jams.
- hard disk when a data transfer is
completed. How Suitable are Event Driven Programs
for Non-Graphical Applications Example - Fire alarms are event driven programs as
instead of the user having to activate
the alarm when there is a fire, the fire
alarm is able to activate itself when it
detects smoke. Why? - They can be suitable because as in
the case of a fire alarm, it activates
itself when the event (the fire) occurs.
- They can also be quite unsuitable as
for CLI (Command Line Interface)
systems (like DOS (Disk Operating
System)), the user needs to remember
operating system commands and
needs to type them in accurately.
Throughout this presentation, I will be explaining: - The different types of event driven programming
- service orientated
- time orientated
- Event Handlers
- Event Loops
- Trigger Functions
- Events
- Examples
- Forms
- Simplicity of Programming
- Ease of Development
- Operating Systems
- How Suitable are Event Driven Programs for Non-Graphical Applications http://maslabmit.edu/2011/wiki/Team_Eleven http://ilyasitnikov.com/2011/03/08/html-beginner-tutorial-how-to-set-up-a-basic-page-skeleton/ http://www.diskmania.co.uk/keyboard-mouse.html http://pennua.org/2010/11/grade-alert-system-is-in-effect/ http://pcservice-repair.net/Virus-Removal.php http://www.colourbox.com/image/blue-large-button-click-here-isolated-on-white-background-image-2186508 http://kddidit.com/myPubs/tutorials/iWeb.php - If they weren't event driven, then the user
input would over-complicate things, as the
application would have to wait for the user's
input to be able to run. - Non-graphical applications would be able
to run faster if they were event driven
instead of user input, as it can be left
without the needs of updates for long
periods of time. http://www.artscondos.com/2011/05/23/fire-alarm-speaker-installation-9th-and-10th-floors-2/ http://en.wikipedia.org/wiki/Operating_system http://www.effingtechnology.co.uk/databases-and-programming.php
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