Mainframe Computers:
They are slower than a supercomputer but they are far less expensive. They may cost around 4 million pounds to purchase.Mainframes can execute billions of instructions per second and can process large amounts of data simultaneously.They are usually connected to a large number of peripherals e.g. printers, terminals, disk drives etc.
They are used by large companies such as:
- Utility companies e.g. gas and electricity suppliers to calculate customer bills.
- Banks - for managing thousands of customers accounts each day
- Insurance companies - for keeping track of policies and claims
- Airlines - for dealing with bookings, tickets, cancellations etc
- Police - for storing and processing all of the data collected each day about crimes
Personal Computers:
The desktop PC has a central processing unit housed in a metal or plastic case (often called a tower unit). A keyboard and mouse are usually used to input data and a monitor to output the data.Until recently, most PCs all looked the same, a very boring beige or grey box. Now manufacturers are coming up with some really interesting designs such as the 'alien' design on the right.Modern PCs are quite powerful. They can carry out millions of calculations per second.
Laptops:
Many workers are no longer 'chained' to their desk. Many people need to be able to move about during their working day. This could be going to different offices or buildings for a meeting or driving to another town for a meeting or conference. It could be that people want to be able to carry on working whilst travelling to and from work on the train.
Personal Digital Assistant (PDA):
A PDA was originally developed as an electronic organiser. They aimed to replace diaries, 'to do'lists and address books. However, rapid development has resulted in palm tops and PDAs becoming almost cut down computers in their own right.PDAs are now available with cut down versions of the main Office software, e.g. Microsoft Word, Excel and Access. The reason they are so successful is that they usually have the ability to synchronize with a desktop PC. So, any work you have been doing on your PDA can be uploaded to your PC and the files updated.Many PDAs can now also access the Internet and can be used to research web pages, send emails or even play games. Some even double up as phones.
Embedded Computers:
An embedded computer is a single chip that contains all of the elements that are essential for any computer i.e.
- RAM
- ROM
- CPU
- Input
- Output
- Clock
Another term often used for an embedded computer is a 'micro controller'. This is because the main purpose of an embedded computer is to control something.
All of the following contain an embedded computer:
- telephones
- televisions
- cameras
- washing machines
- microwave cookers
- dishwashers
- cars
