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Main » 2013 » August » 11 » INTRODUCTION TO COMPUTER
9:12 PM INTRODUCTION TO COMPUTER |
WHAT IS COMPUTER?
A Computer is a device or set of devices that work under the control of a stored program,
automatically accepts and processes data to provide information.
. Automatic: it carries out instructions with minimum human intervention
. Re-programmable: it stores instruction (the program)
. A data processor: it carries out operations on data (numbers or words) made up of a
combination of digits to produce information.
Data is the name given to facts. Information is the meaningful data that is relevant, accurate, up
to date and can be used to make decisions.
A computer accepts and then processes input data according to the instructions it is given. The
elements of any sort of processing are INPUT, PROCESSING, STORAGE, and OUTPUT that
can be depicted as shown in the following diagram.
A Computer operations are performed according to programmed logical and arithmetical rules.
The arithmetical element might be as simple as x + y = z. The logic will be something along the
lines of if x + y does not equal z then add 3 to x and try again.
A Program is a set of coded instructions, which tells the computer what to do. For as long as the
Instructions are being carried out they are usually held in the computers internal storage or
Backing Storage
Output
Device
Input
Device
Main Storage
ALU
Control
CPU
memory. A Computer is therefore a mixture of physical, tangible things like keyboards, mouse,
monitors, internal circuits and communication media referred to as HARDWARE and intangible
things like stored programs referred to as SOFTWARE. Using electrical impulses, the two are
connected and communicate with each other.
1.2 CLASSIFICATION OF COMPUTERS
Computer can be classified into three aspects:
. Representation of numbers
. Degree of specialization
. Types of application
Representation of Numbers
There are three basic aspects of Computers, which are digital, analog and hybrid.
Digital Computer: This aspect of computer operates on numbers directly. It handles numbers
discretely and precisely rather than approximately.
Examples of digital computers are digital watch, digital phone and digital radio.
Analog Computer: This aspect of computer deals with quantities that are continuously variable
e.g. speedometer, electric meter, water meter, thermometer.
Hybrid Computer: This computer combines the features of both analog and digital computers.
They handle data in both quantities and variable.
Degree of Specialization
There are two basic types – special and general-purpose computer.
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Special Purpose Computer: This aspect of computer is designed to perform one or specific
task. The program of this aspect of computer is in-built into the machine permanently. For
instance, special purpose computers are used for solving navigation problems in aircraft and
ships.
General Purpose Computer: These computers have the ability to handle a wide variety of
different programs and to solve many different problems.
Types of Application
There are two types – Scientific and Business Applications.
Scientific Applications: These computers are designed to handle scientific application more
effectively. They require small volume of data input and output.
Business Data-Processing Application: These computers are designed to handle business data
processing applications. They need a large data file, input storage, output storage devices and
large storage capabilities.
1.3 Types of Computers
They are many types of computers and they include:
. Mainframe computers
. Mini - Computers, now often called "Mid-Range" Computers
. Micro - Computers, now commonly called Personal Computers (PC)
. Super computers
Mainframe Computer system is one that has at its heart a very powerful central computer
linked by cable or telecommunications to hundreds or thousands of terminals and capable of
accepting simultaneous input from all of them. A mainframes has many times more processing
power than a PC and offers very extensive data storage facilities. Mainframe Computers are used
by organizations such as banks that have very large volumes of processing to perform and have
special security needs.
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Many organizations have now replaced their old mainframe with network "client server" systems
of Mini Computers and PCs because this approach - called downsizing is thought to be cheaper
and offer greater reliability, functionality and data security than networked systems.
Minicomputer is a computer whose size, speed and capabilities lie between those of a
mainframe and PC. The advent of more powerful chips now means that some 'Super Minis' and
even PCs linked in a network can run more powerfully than small mainframe. The advent of PCs
and with mainframes now being physically smaller than in the past, the definition of a Mini-
Computer has become rather vague. There is really no definition, which distinguishes adequately
between a PC and a mini computers include IBM with its AS400, ICL and DEC.
Micro Computer market was first developed by companies like APPLE COMPUTERS, but a
key event was the launch of the IBM PC in August 1981. In the early year of the development of
the PC, the Apple Macintosh (technically not a PC ) became the standard for graphics - based
applications and the IBM PC and a host of IBM-Compatibles, were chosen for text-based
(business) applications. However, as chips have become more powerful, the difference in
emphasis has become less important. Apple have recently introduced the power PC, which is
IBM-Compatible. PCs are now the norm for small to medium-sized business computers. Today
microcomputers are Personal Computer system or stand-alone computer. They are being
distinguished from other computer systems because of possessing a single microprocessor. Other
business computers are:
. File server
. Portables
. Workstations.
FILE SERVER is more powerful than the average desktop PC and it is dedicated to providing
additional services for users of network PCs. A very large network is likely to use a 'Mainframe'
computer as its server and indeed mainframes are beginning to be referred to as 'enterpriseserver'.
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PORTABLES: The original portable computers were heavy, weighing around five kilograms
and could only be run from the main electricity supply. Subsequent developments allow the true
portability.
a) Laptop is powered either from the electricity supply or using a rechargeable battery. It uses
31/2 disks and CD-ROMs, a liquid crystal or gas plasma screen and is fully compatible with
desktop PCs.
b) The Notebook is about the size of an A4 pad of paper. Some portables are now marketed as
'sub-notebooks'.
c) The Palm Or Handheld Computer, may or may not be compatible with the PCs. They range
from machines, which are little more relatively powerful processors with DOS compatibility and
communications features.
WORKSTATION was originally a computer used by one person, particularly for graphics and
design applications and was used primarily in engineering. It had a fast and powerful central
processor, a high - resolution monitor and large memory. This enabled complex designs to be
easily manipulated.
These characteristics however are no longer unique to Workstations. High performance personal
computer can offer very similar services, so the distinction is a historical one. Personal
computers are generally fitted with some kind of graphics expansion card - a circuit board
containing the necessary electronics.
Super Computer is used to process very large amount of data quickly. They are particularly
useful for occasions where high volumes of calculations need to be performed. For example in
meteorological or astronomical applications, manufacturers of super computers include cray and
fujitsu. They are not used commercially.
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