Computers have been classified
into five (5) different categories viz;
-
Classification by generation (this have been discussed
un the previous notes)
-
Classification by type or mode of processing
-
Classification by size
-
Classification by function
-
Classification by programmability
Classification of
Computer by type of Mode of Processing
There are three types of computer under this category. They are:
1.Digital Computers:
These are computer designed to processed data in discrete numerical form which
are represented by discrete signal using binary code, numbers, letters, and
symbols are represented by codes based on the binary number system consisting
of two digits .i.e. 1,0 the digital computer must convert all data to binary
form. Generally, results from digital computer are more than the results from
analog computers. They are used for counting and calculating numbers. Examples
are calculator, adding machine, counting machine, etc.
2. Analogue
Computers: These are computers that measure the continuous physical magnitude
or electrical states. For example
pressure, temperature, voltage, volume, etc.
For instance a petrol pump at the filling station uses an
analog device to measure the quantity of petrol to the nearest Naira/Kobo and
the quantity of the pumped fuel to the nearest one tenth of a liter. A
speedometer in a vehicle is another example of analog computer
Analog computers are used for scientific, engineering and
process control purposes. Since they deal with quantities that are continuously
varying in nature, they give only approximate result i.e. Not accurate results as in digital
computer. Other examples are the
thermometer, volume control of a TV set meter.etc.
3. Hybrid Computers: These are computers that combine the
features of digital and Analog computers together. They can be used for both counting and measuring.
In fact, they are very useful in the control of manufacturing and processing.
Classification of
Computer by Size
There are 3 type of computer in this category; they are:
1.
Mainframe Computers: These are very large computers
that require extensive space, and they are very expensive to buy and maintain.
They are general purpose in nature and have very large computing power, which
enable them to be capable of handling multiple simultaneous activities like
batch processing, Interactive processing, transaction processing, all other
under the control of an operating system that provide for scheduling and
control facilities. Their main memory is large and a lot of data and
instruction can be stored their.
Their processing speed is high and
they can only be used in large organization or institution where very large
amount of information are been processed like banks, insurance companies,
manufacturing firms, universities, etc. an example is IBM 370.
2
Mini Computers: These are smaller in size than the
mainframes but bigger than the micro computers.
They are less expensive to mainframes computers; as a result, they are
affordable to medium size organizations.
Although, most of them are general
purpose in nature, some are still been used for special or dedicated
purposes. When compared with mainframes,
their processing speed is slower, their main memory smaller and their
capability to support secondary storage system are lower but they are larger in
the same terms than micro computers. They have the ability to handle complex
calculations.
3
Micro Computers); - micro computers are the smallest
and the cheapest when compared with mainframes and mini computers. They are
otherwise known as personal computers (PC) because they are designed as single
user system. Their processing speed
is the highest and their central processing units (CPU) consist of
microprocessors placed on silicon chips.
Present day micro computers are very complex, powerful, rugged, have
very large storage capacity and some of them are very portable as we shall
discuss the types of micro computers now.
Types of Micro Computers
Microcomputers can be further divided into different types
based on the size of their central processing unit (CPU) and other major and
minor components. They are;-
(1) Notebook
Micro Computers; - these micro computers are having their sizes just like the
size of exercise note books. As a result, they are handy.
(2) Laptop
Microcomputers; - these are the microcomputers that can be conveniently
operated on the lap. They are bigger in size and slightly heavier than the
notebooks. They can perform virtually all the function of the desktop
microcomputers, yet very portable like the briefcase size. They can perform complex
task anywhere, anytime with ease. They are expensive compare to other
microcomputers with larger sizes; this is as a result of high technology with
reduction in size.
(3) Desktop
Microcomputers: these computers can be placed on flat smooth tables (desk) for
convenience and comfort ability when in use. They are bigger than notebooks and
laptops. They can also perform various complex operations. Desktop
microcomputers are subdivided into their sub-devices/ parts eg. The keyboard,
monitor, system unit are all separated from one another having cables used for
their connection before use unlike notebooks and laptop where all are
permanently joined (connected) together when manufacture.
(4) Minitower
Microcomputers: these are recent
modification on the system unit, whereby the system unit is made to stand erect
on its own and placed beside the monitor unlike desktop which lies flat on
tables and monitors placed on it. They also have their parts separately having
cables for connection.
(5) Full
Tower microcomputer: These computers are closely related to the mini Tower,
except that they are a bit higher and wider in physical size than the Mini
Tower. All other things are the same as in Mini Tower Microcomputers.
Classification of
Computer by Function
There are two (2) types of computer under this category.
They are
(1)
General Purpose Computers: - These are multipurpose
Computers capable of solving a wide range of problems (task). They can be used
in and for various aspects like drawing, calculating, designing, typing,
multi-media functions, playing games. Etc. Examples are the Desktop computers,
Laptop, Mini Tower computer, etc
(2)
Special Computers: these are dedicated computers
designed solely for the purpose for solving a particular problem. Examples are
the road Traffic Light control, calculators Robots (Robotics), Counting
Machines, etc.
Classification of Computer by Programmability
There are two (2) types of
Computer under this class, they are:-
i.
Programmable Computers and
ii.
Non Programmable Computers
(a) Programmable
Computers: - These are computer designed to accept different programs from
users to solve problems. Computer that are generally suited to carry out such
programming task are programmable computer. Examples are the Micro Computer, Mainframe
Computers. Etc.
(b) Non
Programmable Computers:- These are computers designed to tackle a particular
set of tasks, therefore can not accept any other program from any user apart
from what it is meant for. They are similar to the special/dedicated purpose
Computers. Examples are the Temperature Thermometer, X-ray Machine, Vehicle
Speedometer, Wind Vane Hydrometer, Hygrometer, etc.
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