systems architecture

While returning back from VGSOM on last Thursday i met my friend Pulkit near Cafe Coffee Day..He had come there to grab a quick bite and hence was a lucky coincidence.We sat and ordered our lunch.He asked me how were the studies going on.I told him that i had a class of MIS and that we had a lecture on system architecture..
Pulkit: woohhh...but weren't u studying mba, i mean it sounds technical..
Me: (laughing) bro its basic computer knowledge and doesn't require coding or anything..
Pulkit: hmmm ok but the name sounds scary
Me: no bro not at all..comeon do you want an insight ...
Pulkit : yeah man tell me !!
Me:Ok ..from the scratch..What is system architecture? A system refers to a database which describes what is to be processed and applications which process the data in the database. Architecture depicts the way in which different hardware components are interconnected and which software is running on which hardware. Database is used for storing data which in turn is accessed and processed using a software.
Pulkit: Are there types or examples of these?
Me: Yes definitely.System architecture is of the following types:Single tier, Two-tier: client server architecture, Three-tier architecture and Multi-tier architecture.
Pulkit: cool..so what is the first type?
Me: In the first type i.e the single tier architecture the data and application both reside on the same machine but are logically distinct.you use microsoft word?
Pulkit: yes of curse for making documents and all..
Me: Yes .. The document created and the application that creates it, both reside on the same system.But this architecture has disadvantage.
Pulkit:oh yeah ? what?
Me:Imagine how difficult it will be  for businesses with heavy data and raw applications.
Pulkit: ok so for that we have two tier architecture?
Me:In a two tier or client-server architecture there is a server on which data resides and there are clients where application runs and processes the data.Why is it called client server architecture is because each user has a copy of the application on his own machine, the client machines, but the data – the common data that is used by all- is stored in a common machine called server.
Pulkit:Any examples of this?
Me: Oracle and MySQL
Pulkit: This architecture looks fine right?
Me:Actually not.If there is any modification or updation of  the application software the time taken will be immense.
Pulkit: So we have a 3-tier architecture?
Me: Yes absolutely correct..How did you know that?
Pulkit: Easy to guess in the starting you said there are many types so i took a guess.
Me: ha ha..well done .now i will tell u what it is exactly.In a three- tier architecture, the server which was used to store data in two-tier architecture is now used to keep both data and application in two different sections. This kind of server is called application server. If any change is needed in the business logic then, it is performed in the application server itself.
Pulkit:Then what is the multi tier architecture?
Me:The multi-tier architecture uses the internet and the web browser.Another server is needed called the web server.
Pulkit: ok so what you are telling is we need an internet connection to use this?
Me: yes
Pulkit: but will it be safe?
Me: For safety reasons only we use firewalls.
Pulkit: wow yaar i had never had such an informative lunch before ever.Thanks for telling me so many things and things which i had no idea of.
Me: It was fun isn't it.
Pulkit: Yes defnitely..gotta go to my hostel.
Me: sure catch you in the evening then bye bye
Pulkit: Sure.bye bro.