AQA Information and Communication Technology/ICT5/Communication and IS

Originally, most large organisations had a mainframe with dumb terminals (simply front-ends to the mainframe; they did no work themselves) to use an IT system. Such systems are rare, although old-style ATM's are such an example.

Nowadays, people use distributed processing, where each terminal has its own processing power and does operations itself, rather than relying on a mainframe. Early computers tended to be stand-alone, with no communication.

Standalone computers require their own individual facilities (such as printers), and files on one can not be easily transferred to another system. However, they are more protected from external virii. Networked systems can take advantage of shared resources and easier communication and also tend to be easier to administer.

We covered networking comprehensively in ICT2. You need to know which kind of network to use for a specific application in ICT5.

When considering the Internet, you basically think of it as a series of LAN's which are connected together. Routers sit on the border of each LAN where the links are and announce to the world which IP addresses are on that LAN, and listen for other routers so it knows where to send data to.

Distributed databases
When an organisation is spread out all over the world, it can be expensive to provide network access to a single central database, so databases are distributed.

With a distributed database, only the part of the database that is required for that area of the business is held. However, ensuring data integrity becomes important.

Client/server databases
In the client/server model, a dedicated database machine runs the database server (typically the DBMS). The client machine connects to the server to perform queries and generate reports.