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COMPUTER - 2
K. BARANIDHARAN.M.COM.,M.B.A.,M.PHIL.,PH.D.,
[email protected]@gmail.com
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FLOPPY DISK Floppy disk is a recent development in storge devices it was developed
in 70s
This is very small storage device which can be used both as input and
output medium this is made up elastic plastic material and a finely
coated with magnetic oxide
This disk is placed in plastic cover to avoid damage the floppy is
avaiable in 3 standard size of, storage capacity 8 inches - 250 KB to 1.5 MB
5.25 inches - 125 KB to 1 MB
3.5 inches - 720 KB to 1.44 MB ==FEATURES===
It is small storage medium-easily taken from one place to another place-
cheap storage medium-very useful for PV-both input and output device-
reading and writing-small commercial houses
The floppy is inserted into floppy drive-this rotates inside the floppy drive
like a musical record and the data is stored on fine circular paths called
tracks
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SCANNERS Scanners is an instrument which is used to scan a
diagram, photograph etc., and image can be broughton to the monitor.
The scanner is used light is ON in the scanner,appears on the screen of the monitor, this image canbe edited and shaped into desired from
To use a scanner, a special software is required to beloaded in the computer , the software is generallyavailable with the scanner
Optical scanners are becoming very popular for the
purpose of office automation Now-a-days, computerised bank branches are using
scanners for storing the signatures and photographsof the customers
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OUTPUT UNITS the function of output units is reverse in nature than that of input
unit /input unit is used to fee the data into the computer andoutput unit takes out of the data from the computer-the following
are some devices which are used as output devices:
MAGNETIC TAPE FLOPPY DISK
DAISY WHEEL PRINTER DOT MATRIX PRINTER
LASER PRINTER LINE PRINTER
OPTICAL PRINTER VED DISPLAY UNIT(vdu)
MICROFILM MICROFICHE
TAPES PLOTTERS
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PRINTERS Printers are the output devices
The data/information from the main memory of computer is transferred
to the memory of printer and the same is printed in the form of output.
The data can be printed in the form of graphs, letters, reports etc. as
desired by the user As shown in the figure, the printers are mainly divided into two parts
1. IMPACT PRINTER = Impact printers useRIBBON/CARBON papers to leave an impression on the paper
2. NON IMPACT PRINTER
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Impact
DOT MATRIX PRINTR
The impression of character in the form of DOTS/ahammer which prints the characters one by
one/the output obtained in he form of DOTS/the
hammer of head contains 9 pins or 24 pins
The typical speed of dot matrix printer is 40
characters per second to 1000 characters per
second
The printer mostly print in left to right movement
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LINE PRINTER
Line printers are called so because these printone line at one time/speed of line printers Ismeasured in terms of printing of lines perminute/work on large amount of data printing fora quite longer duration of time
The speed of line printer is wonderful and theycan print 300 to 2500 lines in a minute/the widthof the line is 15 inches and the line has 96 to 160
characters Chain printers and drum printers come in the
category of line printers
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CHAING PRINTERS
In a chain printer, a chain of characters rotates
and in this process hammer of the printer
strikes on chain and the character of the chain
leaves an impression of the character on the
paper
This printer can work for a longer time but the
quality of output is not so good
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DAISY WHEEL PRINTER
This printer contains a disk of metal or plasticand it has 96 characters on its petals /this disk
is capable of rotating/the hammer of this
printer pushes the character and it leaves animpression of the alphabet on the paper
The typical speed of printer is 20 characters per
second to 100 characters per second/cannot beused for longer duration and slow
functioning/superior quality
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Non-impact
LASER PRINTR
The printers generate both graphics as well as textas image output and is very good, use the
technique of laser and photocopy
The speed of this printer is marvelous, print more
than 300 pages in one minute/now ,can print
multicoloured graphis/output
As the quality of the output is very good, laser
printers are used in Desk Top Publishing
Limitations is very costly
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THERMAL MATRIX PRINTER
the printers work on heating arrangement,
special type of paper is needed for printing
it contains print wires and when electricity ispassed through these wires and with passage
of current, the wires get heated and leave
impression with the help of special type of
ribbon
these printers are slow and costly
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INK JET PRINTER
The printer do not make a noise whileprinting/the drops of ink appear in the from ofcharacter/small pumps release tiny drops of inkthough nozzles onto the paper in the form ofcharacter
The printing of this printer is good and a goodquality of graphics can be obtained/speed of ink
jet printer ranges between 50-300 characters per
second The shaped of these printers is very less as
compared to laser printers
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PLOTTERS
Plotters are output devices and are used forvarious purposes like graphics, diagrams etc
Three are different types of plotters and areused for various purposes
1. GRAPH PLOTTER
2. FLAT BED PLOTTER3. DRUM PLOTTER
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GRAPH PLOTTERS
AS EVIDENT FROM ITS NAME, GRAPHPLOTTERS ARE USED IN GRAPHIC WORKANDDIAGRAMS
FLAT BED PLOTTERSTHIS PLOTTER USES ALIGHT PEN AND DRAW GRAPHS ON THEPAPERS/MULTICOLORED PENS ARE USED FOR GRAPHICS/PENIS CONTROLLED BY PEN HOLDER, 8-10 COLOURS ARE USE
THIS PLOTTER IS ALO KNOWN AS light pen plotter IT CANMAKE GRAPHS OF SMALL TO LARGE SIZE DEPENDING UPONTHE SIZE BED
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DRUM PLOTTER
DRUM PLOTTER (PRINTR) CONTAINS A DRUMWHICH IS CYLINDRICAL IN SHAPE/DRUM ISCAPABLE OF ROTAING
DRUM PLOTTER PLOTS THE GRAPHS ON PAPERBY RORATING
NORMALLY A LINE IN PRINTED OUT PUTCONTAINS 132 CHARACTERS AND THIS CAN
PRINT 600-2000 LINES PER MINUTE
THESE PLOTTERS ARE VERY CONSTLY AND ARENOT USED WIDELY
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Visual Display Units(VDU) Model of TV, displayed by Cathode Ray Tube to display a
data, graphics, letters, pictures etc.,/common output
device besides printer, plotter, speaker, speechsynthesizer,etc.,
The keyboard enter the data into the computer and theCRT is used to display the input data as well as the
messages and processed out put from the computer The CRT produces a beam of electrons that makes the
picture on the screen/the raster scan in the VDU andhelps to convert the beam into a picture
Graphic capacities depend on the capacity of the adapter Monochrome and coloured monitors are the two types
of monitors
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CENTRAL PROCESSING UNIT (CPU) CPU is the main part of the computer
In other words it is referred to as BRAIN of the computer
This part of the computer controls all the functions of thecomputer
CPU divided into THREE parts
CONTROL UNIT
ARITHMETICL LOGIC UNIT
(ALU)MEMORY UNIT
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CONTROL UNIT
Control unit, as a evident from the name, controlsthe working of the computer and ascertains
whether the computer is functioning as per the
commands given to it by the user or not
This part is located between MEMORY UNIT
and ARITHMETICAL LOGIC UNIT The data can be transferred between them
though this unit
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ARITHMETICL LOGIC
The function of this unit is to verify
the accuracy of data received from
memory unit and transfers the sameback to the main memory of the
computer
This part performs all arithmetical
and logical functions
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MEMORY UNIT This unit stores data, calculations and results into it and incase of need it sends the data in the form of output
the capacity of memory is measured in terms of BYTES,KILOBYTES or MEGABYTES / the bigger unit is GIGA BYTE
Memory unit transfers the data to ARITHMETICAL and LOGICUNIT.
1 KB = 1024 BYTES
1 MB = 1024 X 1024 BYTES 1 GB = 1024 X 1024 X 1024 BYTES
1 TERA BYTE = 1024 X 1024 X 1024 X 1024 BYTES
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VOLATILE
Memory may be volatile or non-volatile in
nature
Volatile memory is washed a soon as hepower is cut
The informations and the data is also washed
as soon as the power supply is stopped
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NON-VOLATILE
Non-volatile memory is not washed if the powersupply is cut and hence the data and
informations are safe in that memory, mainly
memory of computer is of following types:
1.Read Only Memory (ROM)
2.Random Access Memory (RAM)
3.Programmable Read Only Memory (PROM)
4.Erasable Programmable Read Only Memory (EPROM)
5.Electronically Erasable Programmable Read Only
Memory (EEPROM)
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READ ONLY MEMORY This memory is also termed as FIRMWARE/this memory cannot be altered or
washed and permanent in nature/this memory gives instructions to the
compUter/ROM is non-volatile in nature
RANDOM ACCESS MEMORY memory is temporary/washed as soon as the supply of power is cut/capacity of
computer is related with RAM/more powerful is computer = further divided
into 3 parts = 1.Cyclic 2.Serial Access 3.Direct :-
1.CYCLIC MEMORY:=this memory of the computer transfers the data in cyclic
order/this memory takes more time in transferring the data/the storage devices
like magnetic drums fall in this category
2.SERIAL ACCESS MEMORY:=this memory transfers the data in a serial order/the
data or records are read one by one/hence to reach a requiredrecord/information, we have to pass through the remaining data/this memory
also takes more time in transferring the data and hence more time is wasted in
reading the required data/magnetic tapes store the data on to them in serial
access manner
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3.DIRECT ACCESS MEMORY:=this memory transfers the data in a
direct order and the time in reading the data is less/to read a
particular record\infomation, we have not to pass though the
remaining data/magnetic disks store the data on to them in directaccess manner
PROGRAMMABLE READ ONLY MEMORY this is a type of semi conductor chip on which program can be written
once and only once/this program is written with the help of computer
ERASABLE PROGRAMMABLE READ ONLY MEMORY
this is type of semi conductor chip on which the memory can be erased
with the exposure to ultraviolet radiations
ELECTRONICALLY ERASABLE PROGRAMMABLE READ
ONLY MEMORY:=there are some special chips in the computer thememory on which can be reprogrammed with the help of electronic
signals/the old data can be a newer one
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The following are some important devices which are used for
memory(data storage):=
Magnetic tables/disks/floppy disk/winchester disks/magnetic
drums
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