The computer has passed through many stages of evolution from the days of the mainframe computers to the era of microcomputers. Computers have been classified based on different criteria. In this post, we shall classify computers based on four popular methods.
Objectives
The
objectives of this post are to:
i.
Classify computers based on size, type of signal, operations and purpose.
ii.
Study the features that differentiate one class of the computer from the
others.
Categories
of Computers
Although
there are no industry standards, computers are generally classified in the
following ways:
Based
on operation or working principle or signal type
There
are basically three types of electronic computers. These are the Digital,
Analog and Hybrid computers.
Analog
computer
It
measures rather than counts. This type of computer sets up a model of a system.
Common type represents it variables in terms of electrical voltage and sets up
circuit analog to the equation connecting the variables. The answer can be
either by using a voltmeter to read the value of the variable required, or by
feeding the voltage into a plotting device. They hold data in the form of
physical variables rather than numerical quantities. In theory, analog
computers give an exact answer because the answer has not been approximated to
the nearest digit. Whereas, when we try to obtain the answers using a digital
voltmeter, we often find that the accuracy is less than that which could have
been obtained from an analog computer.
It
is almost never used in business systems. It is used by the scientist and
engineer to solve systems of partial differential equations. It is also used in
controlling and monitoring of systems in such areas as hydrodynamics and
rocketry; in production. There are two useful properties of this computer once
it is programmed:
1.
It is simple to change the value of a constant or coefficient and study the
effect of such changes.
2.
It is possible to link certain variables to a time pulse to study changes with
time as a variable, and chart the result on an X-Y plotter.
Analog
computers are used to process continuous data. Analog computers represent
variables by physical quantities. Thus any computer which solve problem by
translating physical conditions such as flow, temperature, pressure, angular
position or voltage into related mechanical or electrical related circuits as
an analog for the physical phenomenon being investigated in general it is a
computer which uses an analog quantity and produces analog values as output.
Thus an analog computer measures continuously. Analog computers are very much
speedy. They produce their results very fast. But their results are
approximately correct. All the analog computers are special purpose computers.
In
analog computers, data is recognized as a continuous measurement of a physical
property like voltage, speed, pressure etc. Readings on a dial or graphs are
obtained as the output, ex. Voltage, temperature; pressure can be measured in
this way.
An
analog computer is a form of computer that uses continuous physical phenomena
such as electrical, mechanical, or hydraulic quantities to model the problem
being solved.
E.g.:
Thermometer, Speedometer, Petrol pump indicator, Multimeter
Figure:
Thermometer, Speedometer
Figure:
Petrol pump indicator, Multimeter
These
systems were the first type to be produced. It is an electronic machine capable
of performing arithmetic functions on numbers which are represented by some
physical quantities such as temperature, pressure, voltage, etc. Analog refers
to circuits or numerical values that have a continuous range. Popular analog
computer used in the 20th century was the slide rule.
According
to the Merriam Webster Dictionary, computers in which continuously variable
physical quantities, such as electrical potential, fluid pressure, or
mechanical motion, are used to represent (analogously) the quantities in the
problem to be solved are called analog computers.
Digital
computer
Represent
its variable in the form of digits. It counts the data it deals with, whether
representing numbers, letters or other symbols, are converted into binary form
on input to the computer.
The
data undergoes a processing after which the binary digits are converted back to
alpha numeric form for output for human use. Because of the fact that business
applications like inventory control, invoicing and payroll deal with discrete
values (separate, disunited, discontinuous); they are beset processed with
digital computers. As a result of this, digital computers are mostly used in
commercial and business places today.
Figure:
Digital Computer
Digital
computer represents physical quantities with the help of digits or numbers.
These numbers are used to perform Arithmetic calculations and also make logical
decision to reach a conclusion, depending on, the data they receive from the
user.
These
are high speed electronic devices. These devices are programmable. They process
data by way of mathematical calculations, comparison, sorting etc. They accept
input and produce output as discrete signals representing high (on) or low
(off) voltage state of electricity. Numbers, alphabets, symbols are all
represented as a series of 1s and 0s.
A
computer that performs calculations and logical operations with quantities
represented as digits, usually in the binary number system.
Virtually
all modern computers are digital. Digital refers to the processes in computers
that manipulate binary numbers (0s or 1s), which represent switches that are
turned on or off by electrical current. A bit can have the value 0 or the value
1, but nothing in between 0 and 1. A desk lamp can serve as an example of the
difference between analog and digital. If the lamp has a simple on/off switch,
then the lamp system is digital, because the lamp either produces light at a
given moment or it does not. If a dimmer replaces the on/off switch, then the
lamp is digital, because the amount of light can vary continuously from on to
off and all intensities in between. Digital computers are more common in use
and it will be our focus of discussion.
These
computers deal with data in the form of numbers. They mainly operate by
counting and performing arithmetic & logical operations on numeric data.
Such computers are ‘many problems’ oriented.
Hybrid
computer [Analog + Digital]
In
some cases, the user may wish to obtain the output from an analog computer as
processed by a digital computer or vice versa. To achieve this, he set up a
hybrid machine where the two are connected and the analog computer may be
regarded as a peripheral of the digital computer.
In
such a situation, a hybrid system attempts to gain the advantage of both the
digital and the analog elements in the same machine. This kind of machine is
usually a special-purpose device which is built for a specific task. It needs a
conversion element which accepts analog inputs, and output digital value. Such
converters are called digitizers. There is need for a converter from analog to
digital also. It has the advantage of giving real-time response on a continuous
basis. Complex calculations can be dealt with by the digital elements, thereby
requiring a large memory, and giving accurate results after programming. They
are mainly used in aerospace and process control applications.
Various
specifically designed computers are with both digital and analog
characteristics combining the advantages of analog and digital computers when
working as a system. Hybrid computers are being used extensively in process
control system where it is necessary to have a close representation with the
physical world.
The
hybrid system provides the good precision that can be attained with analog
computers and the greater control that is possible with digital computers, plus
the ability to accept the input data in either form.
Hybrid
Computers are a combination of Analog and Digital computers. They combine the
speed of analog computers and accuracy of digital computers. They are mostly
used in specialized applications where the input data is in an analog form i.e.
measurement. This is converted into digital form for further processing. The
computers accept data from sensors and produce output using conventional
input/output devices.
A
combination of computers those are capable of inputting and outputting in both
digital and analog signals. A hybrid computer system setup offers a cost
effective method of performing complex simulations. The instruments used in
medical science lies in this category.
This
is when a computer make is of both analog and digital components and
techniques. Such computer require analog to digital and digital to analog
converter which will make analog and digital data palatable to it.
Digital
computers could not deal with very large numbers and so, a computer with
characteristics of both analog and digital was created which was known as
Hybrid computer.
Post activity:
In
this post we covered types or classification of computer in detail. The topic
is very tricky so repetition of sentences is observed but trust me they are
there for some purpose [they convey other aspects of the topic with same
sentence structure].
If
more detailed information is needed please browse or search the internet for
above terms. All images are from Google search.
Keywords:
Computer, type or classification of computer.
…till next post, bye-bye and take
care.
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