INTRODUCTION
Fran
its definition, computer is said to be an electronic device, capable of
accepting data as input, processes it and reveals it as result known as output.
In our definition, we discover that computers mode of performance are input,
process and output. Computer has its components as hardware and software in
some cases human ware.
Computer
can be classified base on their principles of operation or on their
configuration. By configuration, we mean the size, speed and storage capacity
of computer. There are three (3) types at computers according to their
principle of operation. These three (3) types of computer are:
1. Analog
computer
2. Digital
computer
3. Hybrid
computer
DIGITAL
COMPUTER
A
digital computer is designed to process data in numerical form its circuits perform
directly the mathematical operations of multiplication, addition, division and
subtraction. The numbers operated on a digital computer are exposed in the
Binary system. Binary digits can also be called BITS, which are O and 1, so
that 0, 1, 10, 11, 100, 101, etc. corresponds to 0, 1, 2, 3, 4, 5, etc. binary digits
are easily expressed in the computer circuits by the presence of (N) or absence
(0) of a current or voltage. A series of eight consecutive bit is called
“BYTE”, the eight bit byte permits 256 different “On – Off” combinations. Each
bytes can thus represent one of up to 259 Alphanumeric characters and such an
arrangement is called a “single Byte character set (SBCS); the factor standard
of this extended ASC11 character set. The use of two bytes or 16 units for each
symbol permits the representation of up to 65,536 character or ideograph. Such
an arrangement is called “Double byte character set” (DBCS).
The
operation of a digital computer are carried out by logic circuits which are
digital circuits whose single output is determined by the condition of the
input, usually two or more. Various circuits processing data in a computer
operates in a highly synchronized manner and this is done by controlling then
with an Oscillator which acts as computer clock. Operating at this speed,
digital computer can perform thousand to trillion of arithmetic and logic
operations per seconds.
Before
a computer can be used to solve a given problem, it must first be programmed i.e
by given set of instructions or program. The various programs by which a
computer controls aspects of its operation such as those for translating data
from one form to another is known as “software” as contrast with “Hardware”
which is the physical equipments. In some computer, the moment – moment control
of the machine resides in a special software known as “operating system” (OS)
or supervisor software is at great importance. Hence the usefulness of a highly
sophisticated array of hardware can be served compromised by the lack of
adequate software.
A
digital computer can store the results of its calculations for later use, and
can computer result with other data and on the bases of such computer can
change the series of operation if performs.
Associated
with the central processing units (CPU) or memory where results or other data
are stored ranging from a small fraction of a second days or weeks before being
retrieved for further processing. Once made up of vacuum tubes and later of
small doughnut shaped ferromagnetic cores strung on a wire matrix, each of
which consist of thousands of semiconductor devices. Where each vacuum or core
represents one bit and the total memory of the computer was measured in
thousand of bytes (or kilobytes i.e KB), each semiconductor device now
represents millions of bytes (megabytes i.e. MB) and the total memory of mainframe
computer is measured in billions of bytes (Gigabytes i.e. GB). Random Access
Memory (RAM), which can be read from or written to, is lost each time the
computer is turned off. Read Only Memory (ROM), which cannot be written to
maintains its content at all times and its used to store the computers control information.
Information and program storage, the major materials used today are magnetic
tapes and magnetic disc which can be
read or written on and two types of optional disc, the compact disc (CD) and
the digital dersatille disc (DVD0. DVD is an improved optical storage
technology capable of storing vastly greater amount at data than the CD
technology. CD-read-only memory and DVD-red-only memory discs are impressed
with data at the factory but once being written, cannot be creased and rewritten
with new data. But today both can be rewritten on. Most removable magnetic disc
are commonly made at Mylar enclosed in a paper or plastic holder. Floppy disc
have varying capacity, with very high density disc holding 250 MB to more than
enough to contain a dozen at books. Non removable disc are made at metal and
arranged in spaced layers. They can held more data and can read and write data
much faster than floppies.
Generally,
transferring data is the slowest operation performed by a computer, especially
when received or delivered to human beings. Time sharing used on large
compallows different terminal to use a single computer at the same time. Each
used only has the computer’s used for traction at the time, but the task switching
is so rapid. Most computers in the world are stand-alone, single user device
known as “personal computer” (PC) or workstations. It permits a user for
example to have one file printed and another sorted while editing a third in a
word processing session. Such computer can be linked in a network so that each
computer is connected to others by the wires or coaxial cables, permitting all
to share resources such as printers, modern and disc storage devices.
ANALOG
COMPUTER
An
analog computer is a device that works on continues range at values. The result
given by the analog computer will only be approximated since they deal with
quantities that varies continuously. It generally deals with variables such as
voltage, pressures Temperature, speed e.t.c. The analog system is set up according
to initial conditions and then allowed to change freely. Answers to the
problems are obtained by measuring the variables in the analog model.
Most
present-day electronic analog computer operate by manipulating potential
differences (voltages). Their basic component is an operational amplifier, a
device whose output current is proportional to its input potential difference.
By causing this output current to flow though appropriate components, further
potential differences are obtained and a wide variety at mathematical
operations, including inversion, summation, differentiation, and integration
can be carried out on them. Typical electronic analog computers consist of
numerous types of amplifiers, which can be connected so as to build up a mathematical
expression, sometimes at great complexity and with a multitude of variables.
Analog
computer are especially well suited to stimulating dynamic systems such as
simulations may be conducted in real time or at greatly accelerated rates, thereby
allowing experimentations by repeated runs with altered variables. They have
been widely used in simulations of aircraft, nuclear power plant, and
industrial chemical processes. Other major uses includes analysis of hydraulic
networks (e.g, flow at liquids through a sewer system) and electronics network
(e.g, performance at long-distance circuits).
Analog
computers are commonly found in such forms as speedometers and watt-hour
meters, they largely have been made obsolete for general-purpose mathematical
computations and data storage by digital computers.
Hybrid
Computer
Hybrid
computer are computers that inhibit features of analog computer and digital
computers. The digital component normally serves as the controller and provides
logical operations while the analog component normally serves as a solver of
differential equations. In general, analog computers are extraordinarily fast,
since they can solve most complex equations of the rate at which a signal
traverses the circuit, which is generally an appreciable fraction to the speed
of at light. On the other hand, the precision of analog computers is not good;
they are limited to three or at most, four digits of precision.
Generally
complex equation are approximated using Iterative Numerical methods which takes
huge numbers of interactions, depending on how good the initial “guess” at the
final value is and how much precisions desired. (this initial guess is known as
the numerical seed for the interactive (process)
Digital
computer can be build to solve equation to almost unlimited precision but quite
slowly compared to analog computers. Hybrid computers can be used to obtain a
very good but relatively imprecise ‘seed’ value using an analog computer.