Here is an imaginary conversation with a
friend of mine, who happens to be a student of architecture.
Josh: Hey Vineeth! I have just completed my first “floor
plan”.
Me: Wow!! Let me take a look. It looks like Greek and Latin
to me apart from a few boxes which seem to depict rooms. Luckily for me,
computer architecture diagrams are not drawn to that level of detail.
Josh: Computer Architecture? What on earth do you mean?
Me: Well, it might sound a bit strange, but then, computer
architecture relates to the manner in
which a computer is organized and designed to work.
Buildings are designed in such a way that each room serves a
specific purpose. Take the bedroom, kitchen, bathroom, dining room etc. for instance. In the same way, a computer has
various components and can perform various tasks like playing a movie, users can
create/edit documents, browse the internet, upload and download data from the
internet etc.
For a computer to function the way it does, it must have a
brain that coordinates various functional components and processes data. This
is done by the CPU. But below all of this, we have a computer floor plan which
shows us how the core of the computer is organized.
Josh: Hmm a floor plan? Sounds interesting! Tell me more.
Me: Okay. Assume that your computer is like a house which
you might build in the future. A house will be incomplete without a bedroom, a labyrinth,
kitchen, dining room, drawing etc, each of which serve a unique purpose but all
of which are required together for a building to be considered as a house. Any
of these rooms might serve a purpose on their own but individually they will
not be very useful.
For a computer to function as it does, it needs hardware, an
operating system and software. The computer hardware is comprised of visible physical
components such as the cpu box, monitor, mouse etc.. as well as an operating
system such as Windows 7. The hardware and operating system go hand in hand and a computer would be
useless unless both of these are present. Examples for software could be the MS
office suite, the internet browser, a computer game etc..
A software application is basically a program that performs a
specific/varied set of tasks depending on the requirement. A computer game is
an example of such an application.
All the images, videos and text displayed in the game are
essentially data stored on your computer which is retrieved when necessary by
the software application, in this case, the computer game or by the end user if
he is working on a document.
Josh:I already know most of this. What is so special about
computer architecture? The real world building architecture which I study is the
real deal. It is challenging and not as simple as the computer architecture you
just spoke about.
Me: I am coming to that. Computer architecture refers to the
pictorial representation of the manner in which the hardware and software are
organized and linked to each other.
In the above
example of the computer game your application and data are separate entities,
yet they are linked together in the game. How does this interaction of data and
application take place? This is what the computer architecture indicates.
There are several types of computer architecture, each of
which can be used to meet the objective of a specific requirement. What I have
explained to you via the computer game example is the “Single Tier Architecture”.
This type of architecture is used for personal computers which do not have to
perform a lot of processing and data transfer.
Josh: Single tier architecture? It sounds queer. Do you guys
have 2 tier, 3 tier, 4 tier, 5 tiers architectures for computers?
Me: Actually we do. Let me give you a brief overview on some
of the different types of architecture that computers use.
A single tier architecture
works well when the computer serves a single user. However, when multiple users
need to work on a single document at the same time, it does not make sense to
have multiple copies of the same document on individual machines. It becomes
very difficult to track all the changes and combine these documents. Thus we
need an alternative which allows multiple users to work on the same document at
the same time.
This led to the concept of the "Two Tier Architecture". Here,
the data to be processed i.e. the document is placed on a single system called
the server while all the users have their own individual systems from which
they can access and modify the same document. Only the data is placed on the
server machine while the software application is installed on each of the
individual user machines. All the image processing is performed on the
individual user machines too. Thus the workload is distributed across multiple computers
rather than just one computer in the case of the single tier architecture.
This greatly reduces the processing time of the computer and
results in a faster response.
Josh: This sounds interesting, but how can multiple
computers be made to work together and exchange data in the two tier
architecture?
Me: I was coming to that. The various computers are
connected together by a network which can be imagined as a group of wires
connecting the various systems though this might not always be the case. The
network could be a local area network or maybe even the internet.
For organizations, a three tier or a multiple tier
architecture would be ideal since typically, these organizations would have to
cater to hundreds or thousands of employees and a two tier architecture would
not be ideal for such purposes due to a high bandwidth requirement and since
software updates/version control would be difficult to track over hundreds of
users distributed over multiple geographies.
The three tier architecture has one additional level of
segregation in which, in addition to the data server and individual client machines,
we have a server machine which controls the functionality of the applications
used by the end users and which processes all the data. This server called the
application server is placed between the data server and the client machines. The
data server holds only the data while the end user client systems handle the
user interface for each server.
Thus the distance of data traffic is reduced with an
increase in processing speed and it becomes much easier to maintain software
version control since any major software updates can be made just once on the
application server system.
The 3 tier architecture requires that each end user system
should have a client version of the software installed. However, if the
internet is used as the network, we will just need to use a web browser,
provided that a web server is included between the Application server and the
client machines. This web server functions as a translator between the application
server and the client machines. This is the multiple tier architecture.
Josh: Interesting. I
just have one last doubt. The internet is open to the public. How can organizations
rely on the internet as a part of the computer architecture?
Me: The internet may seem to be an insecure network since
anyone can try to access protected company data, however, we have a software called
a firewall which functions like an internet watchman by preventing external users and hackers from
accessing the data, provided ,the firewalls are configured right.
Josh: Cool. I was shocked when I heard that computers have architectures
similar to buildings, but now, it starts to make sense. Oops, it is time for my
next class. Bye.
Me: Bye
