1.4 Classification of computers

Computers may be compared on the basis of cost, capacity (memory size, data word length, size of secondary storage) and performance (speed).

They may be classed broadly as :

Mainframe computers are very large, often filling an entire room. They can store enormous amount of information, can perform many tasks at the same time, can communicate with many users at the same time, and are very expensive. The price of a mainframe computer frequently runs into the millions of dollars. Mainframe computers usually have many terminals connected to them. These terminals look like small computers but they are only devices used to send and receive information from the actual computer using wires. Terminals can be located in the same room with the mainframe computer, but they can also be in different rooms, buildings, or cities. Large businesses, government agencies, and universities usually use this type of computer. 

Point to be remember: -

1)      Large number crunches

2)      Multi-user e.g. transaction processing for a whole company

3)      E.g. IBM, Fujitsu

Minicomputers are much smaller than mainframe computers and they are also much less expensive. The cost of these computers can vary from a few thousand dollars to several hundred thousand dollars. They possess most of the features found on mainframe computers, but on a more limited scale. They can still have many terminals, but not as many as the mainframes. They can store a tremendous amount of information, but again usually not as much as the mainframe. 

Medium and small businesses typically use these computers.

Point to be remember :-

1)      Small multi-user host

2)      Used by several people in a department  e.g. VAX

Microcomputers are the types of computers, which are generally used in colle.g.es and institute for teaching purpose. These computers are usually divided into desktop models and laptop models. They are terribly limited in what they can do when compared to the larger models discussed above because they can only be used by one person at a time, they are much slower than the larger computers, and they can not store nearly as much information, but they are excellent when used in small businesses, homes, and school classrooms. These computers are inexpensive and easy to use. 

They have become an indispensable part of modern life.

Points to remember :-

1)      General purpose computers

2)       Used by only one person

3)       Desktop size e.g. IBM PC, Mac.

Workstations

Points to remember

• Larger and more powerful

• Single-user still

• Good graphics

• Networked

E.g. Sun, Silicon Graphics

supercomputers

Points to remember

• fastest and most powerful

• used to solve very complex calculations

• multiple processors operating simultaneously

e.g. Cray, Fujitsu