my assignment

[wella.bahingawan]

Synchronous and asynchronous are two big words that seem intimidating 
but are quite simple. Synchronous simply means that all events are 
occurring in a certain time order that can be predicted. A certain 
event would always follow another and they can’t be interchanged. 
Asynchronous is the opposite of synchronous. In asynchronous 
processes, there is no time order. Certain events can, and often do, 
interchange. An excellent synchronous example is music. Each 
participating instrument needs to be in rhythm with the others or else 
the music won’t sound right. For asynchronous, a good example would be 
traffic. Vehicles move at different rates of speed and it is common 
for one to move past another. In most applications, synchronous 
operation is essential as having an asynchronous operation would 
literally mean chaos. Examples of this are railways and airports. In 
these scenarios, it is important to know which vehicle goes first in 
order to avoid collisions. The order of things are carefully planned 
to facilitate a smooth flow and changes to the plan are few and far in 
between. Although synchronous operation is often preferred, there are 
certain cases where it is not needed. There are even cases where 
synchronous operation can be detrimental to the objective. An example 
where synchronous operation is not really necessary is in internet 
browsing. Prior to AJAX (Asynchronous Javascript and XML) most 
webpages need to be reloaded in its entirety to change the information 
on a small section. With AJAX, it is now possible to update that 
certain section while leaving the rest of the page untouched. This is 
beneficial as a smaller amount of data needs to be transmitted and the 
user doesn’t have to endure through the whole page refreshing. AJAX is 
asynchronous because page updates are no longer synchronized. In 
computer operations, I/O is an area where synchronous operation 
becomes detrimental. Synchronous operation in this regard mean that 
the processor needs to wait for the data to be written or read before 
it can continue. The problem is, I/O devices like hard drives and 
especially floppy drives, which have mechanical parts, are very slow. 
If the processor needs to wait for the drive to finish, it would be 
wasting a lot of time. Asynchronous operation allows the processor to 
do other things while waiting for the read/write to finish and just 
carry on once the operation has succeeded.