INTRODUCTION TO COMPUTERS
Definition of the term “COMPUTER” is defined in the Oxford
Computer is an
Electronic Device, which accepts data as input, processes the data and gives
the required information as an output.
The
Characteristics Of Computer
1.
Speed : The speeds with which computers function are measured in Milli
Second (10 3 of a second) ,
Micro-Second (10 6 of a second), Nano-Second (10 9 of a
second) and Pico- Second (10 12 of a second).
2.
Accuracy : The computers are highly accurate in whatever tasks are
programmed to perform.
3.
Diligence : A Computer can continue doing the same job, for a long time (hour
after hour ) and yet produce results which are free of any errors.
4.
High Storage
Capacity : A computer is capable of storing a large
amount of data. The secondary memory consists of various devices such as
Magnetic Disks, Tapes, etc. all of which
will have a very large data storage
capabilities.
COMPUTERS:
THEN AND NOW
This section
gives us the basic information about the technological development trends in
computer in the past and its projections in the future.
The ancestry can be traced as back
and 17th Century, when the first machine capable of performing four
mathematical operations, viz. Addition,
subtraction, multiplication, and division appeared.
Abacus
This was the
first earliest counting devices. It was developed between 1000 and 300 B.C and
used a combination of beads strung on 20 rods to aid counting. Even though the
device is very old, it is capable of giving quick results when used by experts.
Slide Rule
In 1620
William Oughtred invented a calculating device based on the principle of
logarithms introduced by Napier Known as slide rule. It is made up of two
scales which when joined together make it possible to obtain results through
addition, subtraction, multiplication, division etc.
Pascal’s
Calculator
The very first attempt towards this
automatic computing was made by Blaise Pascal. He
invented a mechanical calculator, with lots of gears and chains and used to
perform repeated addition and subtractions.
Leibnitz’s
Calculator
In 1690,
German mathematician Gottfried Leibnitz invented a machine which was based on the Pascal’s Calculator but
was an improvement over it. It was capable of doing, straight multiplication
and addition apart from addition and subtraction.
Jacquards
Loom
Joseph
Jacquard developed an automatic weaving loom which
used punched card instructions for controlling the weaving pattern of the
cloth. The punched cards were held together by a continuous strip and were fed
into the weaving machine automatically.
Difference
Engine
Charles
Babbage developed the Difference Engine around
1822. It was a mechanical device and was used for making the numerical tables.
He used the constant differences to calculate the successive values of the
table.
Analytical
Engine
The design of
the Analytical Engine is superior to the Difference Engine, and had the
capability of solving any mathematical problem. It was developed by Babbage in
1833 and the designs he prepared are widely appreciated even today, as they are
similar to our modern day computers.
We call Charles
Babbage as the Father of Modern Computers. Lady
Ada Auguste who documented all his work assisted him. She was the world’s first
programmer and today we have the ‘Ada
TYPES OF
COMPUTERS
1.
Analog
Computers
They were useful
in measuring humidity, speed, the amount of current flowing etc i.e. for
processing data that vary continuously. It is incapable of taking decisions.
The data is given in continuous form.
2.
Digital
Computers
They perform
calculations by counting. They are widely used at airports, railways ,to
monitor arrivals & departures & also been widely used by banks &
govt. organisations.
Digital
Computers are of two types.
a)
General Purpose :
Classifications depending upon the speed & the power of the
computer.
b)
Special Purpose Computers : It is made for carrying out specific
tasks & is designed
keeping these tasks in mind.
c)
Hybrid Computers :
They incorporate the best features of both Analog & Digital
computers. They can be used in all such problem areas where
continuous & digital processing is required.
GENERATIONS
OF COMPUTERS
(a)
First
Generation ( 1942 – 1958 ) : The First Generation
of digital computers were built using vacuum tube logical circuitry. The size
of the computer was very big, failure rate was very high and reliability was
very low. It had no external memory, internal storage was very limited &
only the machine language could be used. The speed of this computer is measured
in milli-seconds (thousandth of a second).
(b)
Second Generation
( 1959 – 1964 ) : The Second Generation of the
computers were built using transistors. It had magnetic tapes and punched
cards, internal storage was limited. The languages used were Fortran and Cobol
& were operated for scientific commercial purposes. Its size was large,
failure rate was high and reliability was low. Its speed was measured in
microseconds (millionth of a second)
(c)
Third
Generation (1965 – 1970) : The Third Generation
computers was built using I.C. (Integrated Circuits). It had magnetic disks and
drums, internal storage was good. The languages used were Fortran IV and Cobol
68 & were operated for administrative purposes. Its was medium in size,
failure rate was very low and reliability was high. Its speed is measured in
nano-seconds (billionth of a second).
(d)
Fourth
Generation (1971 onwards) : The Fourth Generation
computer was developed using L.S.I.C. (Large Scale Integrated Circuit). It had
magnetic disks and drums, internal storage was very high. The languages used
were Fortran 77 and Cobol 74 & were operated for commercial purposes. Its
speed was measured in pico-seconds (10 12 of a second).
CLASSIFICATION
OF COMPUTERS
Ø Microcomputer or Personal
Computer : This computer is capable of performing large number of functions
like retrieving data, processing and storing results and outputting the
required results. It had a silicon chip which produced all the fuctions and
hence it has named Microcomputer.
Ø Minicomputer : These
are slightly larger than micros and have higher processing speed as well as
higher data storage capacity.
Ø Mainframe Computer : A
very large general-purpose computer, its capacity and processing power is
higher than a minicomputer.
Ø Supercomputer : A very
powerful mainframe computer and for high-speed mathematical tasks.
DATA,
PROCESSING, AND INFORMATION
Data is a collection of facts, figures and statistics, which can be
processed to produce Information. For e.g. In an education environment, data
can be names of students, roll numbers, marks obtained and so on.
Processing is
manipulation of facts, figures & statistics. In simple words it is nothing
but manipulation of data. Some of the operations involved in processing are :
(a)
Calculation : Addition, Subtraction,
Multiplication, and Division .
(b)
Comparison : Equal to, Greater than, Less than,
Zero, Positive, Negative.
(c)
Decision
making : Branching on different path
depending on whether some
condition is true or false.
(d)
Logic : Processing is not
restricted to numbers only. Text also can be
processed so that correcting errors in a document does not
require retyping.
INFORMATION
Information is
data, which is summarised in the way you want it. In other words it is nothing
but processed data.
COMPUTER
SYSTEM
COMPUTER SYSTEM |
|
HARDWARE
|
|
SOFTWARE
|
|
HEARTWARE
|
Hardware: It includes the entire physical components that make up a computer
system.
Software: It is a set of detailed
step by step instruction, called programs, that enable a computer system
perform its assigned tasks.
Heartware: It is person who schedules and operates the hardware, writes and
modifies the software.
HARDWARE
Functional
Units Of A Computer System
The functional
components of a computer system consists of :
a)
C P U (Central
Processing Unit) : It is considered as the brain of the computer. It consists
of three major parts – CU (Control Unit), ALU (Arithmetic and Logic Unit).
Arithmetic
and Logic Unit : It performs calculations and
comparisons required. The data is transferred from the main store to ALU and
appropriate operations like addition, subtraction etc are done as per signals
received from the CU.
Control
Unit : It functions in a fetch-execute cycle. It
fetches the instructions from the main store and decode them and produces the
signals that carry out the instruction.
Input data,
programs, intermediate results, and final results ready for the output are
stored in the Main store.
b)
Peripheral
Devices
Peripherals
Devices consists of three major types :
(i) Input
Devices (ii) Output Devices (iii) Backing storage Devices
Input
Devices : Allow the user to get data into the
machine. The Input Devices available are :
a)
Keyboard b) Mouse
c) OCR (Optical Character Reader) d) OMR (Optical Mark Reader) e) MICR (Magnetic Ink Character
Recogniser) f) Barcode Reader etc.
Output
Devices : Peripheral used to return results to the
user. They include Printers, Plotters, VDUs (Visual Display Unit).
Backing
Storage : The Secondary storage devices like hard
Disk, Floppy Disk, Magnetic tapes etc.
STORAGE
DEVICES
RAM : Read / Write memory called as Random Access Memory. It is a
temporary memory because it looses off data in it when the power is switched
off.
ROM : Read Only Memory where data is hard-wired into chips at the time
of manufacture and is read randomly but can’t be written into.
PROM : Programmable Read Only Memory allows the entering of frequently
required microprogram on to a ROM.
EPROM : Erasable Programmable Read Only Memory is a type of PROM, the
contents of which can be erased by exposing it to the light and the new program
can be placed on it.
EEPROM : Electrically Erasable Programmable Read Only Memory.
EXTERNAL
STORAGE DEVICES
External
Storage or External Storage Devices are mainly hard disks, floppy disks and
tapes used for permanent storage of programs or data.
Hard Disk : This is sealed rigid magnetic oxide medium disk. Hard Disks are
not removable from the drive and since they are sealed dust and other
contamination which are likely in a floppy disk are minimised. These provide
substancially faster data access compared to the floppy disk and provide very
large data storage for on-line retrieval.
Floppy Disk
: Floppy disk becomes a convenient recording medium
to transport information from one location to another. Disk is removable from
the reading device attached to the computer and therefore provides unlimited
storage capacity. The floppy disks of today are available with 3.5 inches and
their capacity is 1.44 MB.
Magnetic
Tapes : They are used to store large volumes or
backup data. These are cheaper and since these are removable from the drive,
they provide unlimited storage capacity. Since recording is like that in a tape
recorder used in the audio systems, information retrieval will be only
sequential and not random. These are not suitable for on-line retrieval of
data, since sequential searching will take long time. These are convenient for
archival storage for backup.
CD-ROM (Compact Disk Read Only Memory): CD-ROMS are very good for
distributing large amount of information or data to large number of users. The
main advantages of CD-ROM are a) Large data/information storage capacity and b)
These are removable and thus are suitable for archival storage. The
disadvantages of CD-ROMs are a) It is read-only, therefore, cannot be updated
and b) Access time is longer than that of a magnetic disk.
INPUT AND
OUTPUT DEVICES
Input
Devices: Input Devices are required to get raw data
into the computer. Some of the input devices are:
Keyboard: The keyboards resemble typewriters keyboard, but also have
additional keys, handling control functions. The computer keyboard is divided
into three parts.
¨ The alphanumeric keys
¨ The special keys
¨ The function keys
The
Alphanumeric Keys of the main keyboard are used to input most of the letters
(A-Z), (a-z), numbers (0-9) and other characters like space , . / ? > < '
" : ; * & ^ % $ # @ ! ( ) + = _ - { } [ ] | \ required for entering
data and programs.
The Special
Keys perform specific tasks instead of inputting characters in the computer
like the Enter or the Return key, the Backspace key, the Delete key, the Insert
key, the Shift keys, the Caps Lock key, the Num Lock key, The Tab key, The Alt
key.
The Functional
keys are used perform a set of operations by a single keystroke. Different
programs use the function keys in various different ways. Some programs allow
the user to configure the function keys according to his or her convenience.
Mouse: A small device containing tracking ball at its bottom. A mouse can
be rolled across a flat surface, which moves the tracking ball thus,
transmitting pulses according to its motion. The mouse has additional buttons
on it to facilitate other functions like pointing, selecting, and dragging.
There are much
more such devices such as :
a) Joystick b) OCR c)
OMR d) MICR e) Barcode Reader
OUTPUT
DEVICES
Output Devices
send out processed information. Some of the Output Devices are :
a) VDU b) Printer c) Plotter
VDU ( Video
Display Unit ): Contains a cathode ray tube (CRT)
which forms the output unit. They are read text information, graphics,
diagrams, and pictures. Graphic display is made up of a series of dots called
'pixels' (picture elements) whose pattern produces the image.
PRINTER: The screen output is taken on a paper with the help of printer.
Printers are again many types e.g. a) Character Printer b) Line Printer c)
Page Print
Character
Printer: Prints one character at a time. There are
so many different types of character printers and some of them are dot matrix
printer, ink jet printer etc. It consists of a set of needle - like points
arranged on the print head, making of a matrix of dots.
Line
Printer: Line Printers print one line at a time.
Line Printer has much higher speed compared to that of a Character Printer.
Page
Printer: Page Printers print one page at a time.
Laser Printer is an example of Page Printer. This will produce a high quality
printing.
SOFTWARE:
The computer
components or the hardware cannot accomplish anything without instructions and data which are referred
to as software.
Computer
Languages:
Computers do
not understand English and hence one must communicate with them in a language
they understand. So, the instructions for an application are written in computer languages. While there
are many computer languages, the commonly used computer languages are BASIC (Beginners
All Symbolic Instruction Code), COBOL (COmmon
Business Oriented Language), C, PASCAL etc. The people who
write these instructions are called application programmers. The program which
is in any of the computer languages has to go through the process of compilation. The compilation
process is done by a software referred to as the compiler. The compiler is a set of instructions which are
used to convert any application program written in a computer language (like
COBOL, C etc.) into the equivalent native language of the computer and saved on
the disk as a program file, which can be used for processing whenever required.
Operating
System (OS): The Operating System software controls
the overall activities of the computer. The operating
system software is a large collection of software which manages the
resources of the computer.
Application
Programs: The programs written by the application
programmers, which satisfy a specific task. COBOL, PASCAL, C etc are the
examples of the Application Software. For example, the language COBOL is used
for the business purpose and the language PASCAL is used scientific application.
Other
Application Programs: Apart from the programs
written by the application programmers, which satisfy a specific task, an
organization may use generalized application packages like a word processor
(MS-WORD), electronic spreadsheet package (MS-EXCEL) etc.
MEMORY
CAPACITY
Bytes are used
to measure the amount of information a device can store.
Byte: One byte is one character. A character can be a number, letter, or
symbol.
Kilobyte
(K): One kilobyte = 1024 bytes or 1024 characters.
Megabyte
(MB): One megabyte = 1024*1024 bytes = 1,048,576
bytes = 1,048,576
characters.
Gigabyte
(GB): One giga byte = 1024*1024*1024 bytes =
1,073,741,824 bytes =
1,073,741,824
characters.
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