Chapter 15 Basic Concepts of a Computer System
1. Basic Concepts of a Computer System
A computer system basically consists of three basic components: Hardware, Software and
data.
Hardware is the equipment associated with a computer system. It is something that you
can physically touch. Software is the computer program that drives the hardware.
Data are facts and numbers only. A computer program is a set of instructions. Programs
can be used to process data into information (application programs and system programs).
It can also be used to control the operation of hardware (drivers).
2. Classification of computers
Computers can be classified according to their capacities and physical sizes. They are
microcomputers, minicomputers, mainframes and supercomputers.
Microcomputers
Microcomputers include personal computers (PC), workstations, portable computers and
palmtop computers.
PCs are widely used now and it is becoming more and more powerful. In the past, PC had
limited capacities and might not be able to do complicate applications.
The difference between a PC and a Workstation is that a PC is a “complete” computer
system, which means a PC has its input and output devices, central processors and storage
devices. However, a Workstation may consist of input and output devices only. This kind
of Workstation is called “dumb terminal” sometimes. It must connect to the server
(usually a minicomputer or mainframe). An example will be the terminals used by bank
tellers.
Nowadays, Workstation has a new interpretation as “powerful PC” because the
configuration of a Workstation is usually better. Also, a PC can handle the tasks of a
server because of its power.
Portable computers include laptop computer, notebook computers and palmtop computers.
Basically laptop and notebook computers are the same but laptop computers are heavier.
The sizes of these computers are small enough to be put in a briefcase and thus they are
portable. Although they are small in size, their powers are as high as PC and Workstations
because of the advance technologies.
Personal organizer is a new type of computer. It is not a full power computer but it helps
people in arranging meeting and store contact information. Some simple applications can
be run on personal organizers now.
Minicomputers
Minicomputers can usually larger in size and more powerful than PCs. A minicomputer
may consist of several functional units. Medium size companies may use it as a server of
a small network.
Mainframe computers
Mainframe computers are even larger in size. Usually they are composed of several units
and central processors. Large organizations such as a department in government,
university and banks will use mainframe computers. Mainframe computers are used as
the central unit of a large network and they can support multi-user and multiprocessing
mode.
Supercomputers
Supercomputers are the most powerful computers now. They are widely used in weather
forecasting, war simulation and national defense and scientific research such as
simulation of nuclear explosion. There is one supercomputer in the Hong Kong
Observatory.
This kind of classification was invented in the 1960’s when the physical sizes of the
computers are quite different. However, there is not much difference between
microcomputers and minicomputers.
There is another kind of classification: general purpose computers and specific purpose
computers (or dedicated computers). A general purpose computer can be used in various
situations and depending on the application software, it can perform different tasks. PC is
considered as general purpose computer. On the other hand, A specific purpose computer
is designed to perform a specific task. For example, the POS terminal in the supermarket
and the Automatic Teller Machine (ATM) are specific purpose computers. A POS terminal
is designed for inventory taking as well as a cash register. An ATM is only used for
performing bank transactions.