1. • Events are an important part of Alice
programming, allowing the creation of interactive
worlds with keyboard and mouse user controls.
• Most modern programming languages allow
programmers to add events to new software.
• Events can be used for many other purposes, such
as controlling burglar alarms, checking remote
sensors, or checking for system events, like
printers running out of paper.
• Events are an important part of modern computer
programming.
In computer programming, event-driven programming is a
programming paradigm in which the flow of the program
is determined by events such as user actions (mouse
clicks, key presses), sensor outputs, or messages from
other programs/threads. Event-driven programming is the
dominant paradigm used in graphical user interfaces and
other applications (e.g. Javascript web applications) that
are centered around performing certain actions in response
to user input.
Event Driven Programming is a computer programming
paradigm. Events are the actions that are performed by the
user during the application usage. If a user clicks a mouse
button on any object then the click event occurs. If a user
moves the mouse then the mouse move event occurs.
An event driven programming is a flexible way to allow
the programs respond to many different inputs or events.
This is a programming in which the primary activity is
reaction to the receipt of semantically significant signals.
The signals can be from any source, and most commonly
including timers, human input, sensors, observation upon
shared state, or can be produced during computation when
it react with other signals.
HOW EVENTS WORKS IN EVENT DRIVEN
PROGRAMMING :->
An event occurs whenever an event listener detects an
event trigger and responds by running a method called an
event handler. Modern operating systems and
programming languages contain facilities to let
programmers set up event listeners.
An event trigger can be almost any activity or condition
selected by the programmer, such as a mouse movement,
someone pressing the enter key, or a bank account balance
changing.
EVENT HANDELER :->
An event handler is a method that is activated when the
event trigger occurs.
Almost any method can serve as an event handler, such as
those that play sounds, initiate data communications, or
perform calculations.
EVENT DRIVEN PROGRAMMING

2. USE OF EVENT :->
1. Events can be used to control objects moving in 3D
space.
2. Detect when some object moves
3 .Detect when two objects collide
4. Make objects move in response to mouse or keyboard
commands.
EVENT TRIGGER :->
An event trigger can be almost any activity or condition
selected by the programmer, such as a mouse movement,
someone pressing the enter key, or a bank account balance
changing.
FLOW OF PROGRAMME :->
PROGRAMME CAN BE WRITTEN IN FOLLOWING
MANNERS :-
Public Function Read() As String
Dim s As String
Dim c As Char()
Dim i As Integer;1]
7k;0]
GetType (CommControl)
m c(read8ufferPosition)
For i = 0 To readEufferPosition — 1
c(i) = ChrW(readEuffer(i))
Next
readEufferPosition = 0
s = New String(c)
End Synctock
Return s
End Function
Private Sub eventThread()
Dim r As Integer

3. PROGRAMMING FLOW IN EVENT DRIVEN
PROGRAMMING :->
PROGRAMME IN EVENT DRIEVEN
PROAGRAMMING :->
WHAT IS DIFFERNCE BETWEEN OBJECT
ORIENTED PROGRAMMING,PROCEDURE
ORIENTIED PROGRAMMING AND EVENT DRIVEN
PROGRAMMING ?
Procedural Programming simply put is dividing your
problem into smaller parts (utilizing the Divide and
Conqure Law) and then representing each smaller part by
a definitive and exact sub-routine/function/procedure.
Hence you look at the code as a big pile of different
procedures that are coupled with each other, one calling
the other, or one calling many while some not calling
anything but rather doing specific computations and
returning the results. Event Driven?!
do not believe there is such a method that stands alone,
Event driven is a charactaristic rather than a development
approach. Object Oriented Programming (OOP) looks at
your problem ad breaks it down to different objects, each
object has consists of a number of elements, called
Members and Methods. (i.e variables and functions
respectively) so your problem is then defined as the
different objects working together and inside each other
sometimes in a closely coupled manner. the conclusion is,
OOP deals with objects and operations on those objects,
where as procedural development breaks down
computation to little pieces.
Event oriented programming cab be written using any
language like c++ or c or any programming language .but
mainly visiual basic is used to write a programs in event
oriented programming .

4. USES OR APPLICATION OF EVENT ORIENTED
PROGRAMMING :->
Event-driven programs are typically used in graphical user
interfaces (GUI) and multi-tasking/multi-threaded
environments.
The operating system maintains a message queue
containing events generated by all active applications and
services.
Every message has an ID denoting the target application,
along with the ID of the event itself plus any data that is
relevant to the event.
When an application is idle, it enters an idle loop which
repeatedly checks the first message on the queue.
If the application ID matches, the message is dequeued
and processed. If the ID does not match, the idle loop
terminates.
Since ever application is given an allocated time-slice of
the CPU according to its priority, so long as the
applications are idle during their allotted time then all
messages will be processed fairly rapidly. However, if an
application is busy and the first message in the queue is
intended for it, that message will effectively block all
other messages to all other applications.
The operating system will appear sluggish because
messages are being enqueued all the time but the busy
application is preventing them from being processed.
To prevent this programmers must periodically yield
control to the system during an intensive process to allow
messages to be enqueued, and then enter idle mode to
process any pending messages.
Once it has dealt with those messages it can continue the
intensive process until the next yield point.Since events
can be posted from one application to another,
applications must be prepared to deal with them.
For instance, if the user chooses to shut down the system,
every application will be notified that it must close.
But if the application is running an intensive operation
then it will not be possible to close the application until
that process has been aborted gracefully.
There are various ways of dealing with this but generally
the application will override the idle loop in order to filter
messages.
That is, the override will dequeue messages but will not
process them unless certain conditions are satisfied. This
is known as "eating" events.
If the event is an instruction to close the application but a
process is still running, then the idle loop will store the
event and set an abort flag that the process can check at
each yield point, allowing it to terminate gracefully.
When the idle loop determines there is no running process
but the abort flag has been set, it will reset the abort flag
and repost the event it stored which can then be dealt with
normally
Most modern computer programs that people use have
Graphical User Interfaces (GUIs).
A GUI has icons on the computer screen and a mouse (or
other device) to control a pointer that can be used to
operate the computer.

5. Modern GUIs like the Word 2007 interface require the use
of event-driven programming.
ADVANTAGE :->
- It allows for more interactive programs. Almost all
modern GUI programs use event driven programming.
- It can be implemented using hardware interrupts, which
will reduce the power used by the computer.
- It allows sensors and other hardware to easily interact
with software.
DISADVANTAGE :->
- For simple programs, event driven programming is often
more complex and cumbersome than batch programming.
- The flow of the program is usually less logical and
obvious.
CONCLUSION :->
There are many uses along with pros and cons when it
comes to Event Driven Programming. One Advantage is
flexibility; in fact you could say that event driven
programming is one of the most ‘flexible programming
language types.’ One of the main reasons being why it’s
flexible is its allowance to let the user design the program
in sections. In other words the programmer is given the
main control over the program in terms of they instruct the
program to do and also the time in which they what this to
happen. ‘Suitability of the graphical interface’‘Simplicity
of Programming’‘Ease of Development’
REFERENCE :->
http://en.wikipedia.org/wiki/Event-driven_programming-
2.http://wiki.tcl.tk/1772--
3.http://searchcloudapplications.techtarget.com/definition/
event-driven-application---
4.http://eventdrivenpgm.sourceforge.net/