History Of Computer-1

8/7/2019 History Of Computer-1

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Unit 1 Data & Information.

Data Processing.

Characteristics of Computer.

Generation of Computers.

Organization Of Computers.

Input& Output Devices.

Storage Devices.

File Organization.


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Hemant 16 85 it is a data and if thesame data is processed and presentedin a particular format it becomesinformation.

Name Age Marks

Hemant 16 85.


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Information It is the processed form of data.

It is obtained after applying a process(like arranging in a table) on data.

Some conditions will be applied onevery data items and the results will bepresented as information.


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Features of Information RELEVANE: Information is good only if

it is relevant. By the term relevantmeans the information is useful andmeaningful to the decision maker.

SUBJECTIVITY: The usefulness and

value of information are highlysubjective. As the same informationmay have different meanings to

different people.


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Features of Information TIMELINESS: The information can

prove worth only if it is delivered to

right person at right time and at rightplace.

ACCURACY: Every piece of information

must be 100% correct in order togenerate correct results. This is becausea piece of information may serve asdata for some other process. To

generate correct output the correct


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Phases of Data Processing1. Data Collection: The first step of data

processing is to decide what data are

needed to generate a result. Data can be collected from both internal

and external resources.

It can be taken manually or by electronicmeans.

It can be collected from service, interviews,documents, news papers or any other

means.


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Phases of Data Processing4. Sorting: The information stored in different

files may be sorted in a desired order to get

the required results.5 .Summarizing: When results are produced it

should be summarized in such a manner thatthey become easy to understand.

6. Reporting: The final stage of data processingcycle is reporting the information in desiredway. Ex: Sales report, Financial reports,Production Cost.


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Characteristics Of Computer Automatic: Computer are automatic

machine because once started on a jobthey carry on until the job is finishedwithout any human assistance.

Speed: It can perform in a few seconds.

Units of the speed are micro sec 10-6neno 10-9 sec and even pico 10-12 sec.


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Characteristics Of Computer Accuracy: It can perform thousands of

operations with great accuracy.

Reliability: Its output is reliable if the i/pdata and instructions are reliable andcorrect.

Storage Capacity: It can store a millionsof characters in condensed form.

Diligence: It can work for hours withoutcreating errors.


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Characteristics Of Computer Versatility: It is capable of performing almost

any task.

No I.Q.: Its I.Q. is zero. It can not determinewhat task it has to perform. It can not takeits own decision.

No feelings: It has no feelings as they are

machines. Power of remembering: It can store and

recall any amount of information because ofits secondary storage device.


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History Of Computer Abacus

Jacquard Loom

Charles Babbages Difference Engine

Hollerith Census Tabulator

Von Neumann


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Abacus An abacus is a calculation tool, often constructed as a wooden

frame with beads sliding on wires.

The Chinese abacus is typically around 20 cm (8 inches) tall and it

comes in various widths depending on the application. It usually

has more than seven rods. There are two beads on each rod in theupper deck and five beads each in the bottom for both decimal

and hexadecimal computation. The beads are usually rounded

and made of a hard wood. The beads are counted by moving them

up or down towards the beam.

The abacus can be reset to the starting position instantly by a

quick jerk along the horizontal axis to spin all the beads away

from the horizontal beam at the center.


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Charles Babbage Difference Engine

The first device that might be considered to be a computer in themodern sense of the word was conceived in 1822 by the eccentric

British mathematician and inventor Charles Babbage.

. Babbage realized that a machine could do the work better and

more reliably than a human being. Babbage directed the building

of some steam-powered machines that more or less did their job,

suggesting calculations could be mechanized to an extent.

In Babbages time numerical tables were calculated by humanscalled computers. At Cambridge he saw the high error rate of

the people computing the tables and thus started his lifes work in

trying to calculate the tables mechanically, removing all human

error. He began in 1822 with what he called the difference engine,made to com ute values of ol nomial functions.


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Technical Evolution Of Computer

First Generation 1950s

Second Generation 1960s

Third Generation 1970s

Fourth Generation 1980s

Fifth Generation 1990s


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First Generation Computers The vacuum tubes were used in the circuit of these

computers.

The input and output operations where done using

punched cards technology. For external storage, magnetic tapes where used.

The machine was capable to do one job at a time,therefore batch processing was adapted.

The operations like setting of switches has to be done

by humans. The language used by these computers was machine

language and assembly language.


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Some computers of these generations are given below:

ENIAC EDVAC

EDSAC

UNIVAC

ADVANTAGES of 1st Generations

Computers

1) The major advantage of vacuum tube technology

is that it made the advent of electronic digitalcomputers.

2) Vacuum tubes were only electronic devices

available during those days which made

computing possible.


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Limitations of First Generation Computers

Not reliable.

Frequent breakdowns where common.

Electric consumption is very high. This type of computers generate too much heat,

therefore air conditioners are required.

Slow Input/Output operations.

They were bulky and required large space.

They have small primitive memories and noauxiliary storage.


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Second Generation Computers

Transistor takes place of vaccum tubes.

Faster than first generation.

Assembly language is used instead of machine

language.

Generate less heat

Smaller in size Magnetic tapes and disks are used.


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Third Generation Computers

Transistors is replaced integrated circuits

Increases speed as well as reliability.

Uses multiprogramming operating system

Lower power consumption

Magnetic disk can be used as a secondary storage.


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Fourth Generation Computers

Very large scale and ultra large scale integrated

circuits has been developed.

Computers now becomes portable.

Semiconductor can be used as primary storage.

Database Management system can be used

Distributed data processing.


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Fifth Generation Computers

Fifth generations computers are only in the minds of

advance research scientists and being tested out in the

laboratories. These computers will be under Artificial

Intelligence (AI), They will be able to take commands in a

audio visual way and carry out instructions. Thesecomputers will perform many of the operations, which

require low human intelligence.

Parallel Processing is coming and showing the possibility

that the power of many CPU's can be used side by side, andcomputers will be more powerful than those under central

processing. Advances in Super Conductor technology will

greatly improve the speed of information traffic. Future

looks bright for the computers.


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Input Unit

Output Unit

C.P.U

Input

Data

Output

Information

Memory Unit

Control Unit

A.L.U

C.P.U. Central Processing Unit

A.L.U. Arithmetic Logic Unit


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Input Unit For the computer to work upon you need to give

instructions as well the data to work upon.

These devices translate data from human

understandable form into electronic impulses

which are understood by the computer.

The common input device is the keyboard.

These device is similar to the normal typewriter,

using which programmers types the instructions for

any task he want to do.

These instructions are called programs.


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Central processing Unit

Once the data is accepted it is fed into the central processing

unit before the output is generated as data has to be processed,

which is done by CPU.

This unit of the computer is the brain of computer system,which does all the processing, calculations, problem solving

and controls all other functions of all other elements of the

computer.

The CPU consists of following 3 distinct units namely : The Memory Unit

The Control Unit

The Arithmetic & Logic Unit


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Memory Unit

This is the unit where data and results are stored.

The major function of this is to remember theinstructions and data.

The data stored can be accessed and used wheneverrequired by the CPU for necessary processing.

This unit consists of cells which are capable to store

unit of information. These cells can be accessed as they are numbered

sequentially, which are called addresses.

This memory unit is usually referred as primarystorage section.

The units in which memory unit is measured areknown as BYTE.

A BYTE is the space required to store one characteror alphabet or digit or any other special character.


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Control Unit This is that unit of CPU, which coordinates all the

activities of each and every element of computer.

It decodes the instructions given by various users and it

sends commands and signals that determine the

sequence of various instructions. Though this unit does

not process data , but it acts as the central system for

data manipulation, as it controls the flow of data to and

from the main storage.


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Output Unit After processing the data, the computer has to provide the

result of the processing to the user.

For this , computer uses output devices.

The output device is that device which is used to provide the

user with desired output.

Commonly used output devices are VDU (Visual Display

Unit) i.e. monitor, printers (line printer, character printer

etc.), plotter, magnetic media like floppy, hard disks etc.

Thus computer performs all the required functions and

processing using the above units. We can say that these

units are integral part of a computer system.


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Input Devices

These are those devices, which facilitate a user to give input.Information is entered in to a computer through input devices.

An input device converts input information in to suitablebinary format, which can be accepted by the computer system.

The computer system has to process details of each

command, therefore the command will have to be converted into machine readable format and this work can be done throughinput unit.


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Working Of A Keyboard

When a key is pressed, it pushes down on a rubber dome

sitting beneath the key. A conductive contact on theunderside of the dome touches a pair of conductive lines onthe circuit below.

This bridges the gap between them and allows current to

flow. A scanning signal is emitted by the chip along the pairs of

lines to all the keys. When the signal in one pair becomesdifferent, the chip generates a "make code" corresponding to

the key connected to that pair of lines. The code generated is sent to the computer through a

keyboard cable.


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A chip inside the computer receives the

signal bits and decodes them into the

appropriate keypress. The computer

then decides what to do on the basis of

the key pressed. Eg: Either display a

character on the screen, or perform

some action.


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Mouse

Mouse is a device which is used to move the cursor on thescreen and to select options.

When the mouse is moved on the surface the cursor is alsomoved in the same direction on the monitor.

By moving the mouse the user can point to menu on thescreen i..e. Mouse is also known as pointing device.

Pressing the button of a mouse is known as clicking.Technicians often describe mouse speed in DPI(dots perinch).

One DPI is intended to be the number of pixels the mousecursor will move when the mouse is moved one inch.

Some common types of mouse are

Mechanical Mouse

Optical Mouse


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Joystick

A joystick is also a pointing device.

It is used to move cursor on the CRT screen.

A joystick is a stick that has spherical ball at its upper aswell as its lower end.

The lower spherical ball moves in a socket.

The electronic circuitry inside the joystick detects andmeasures the displacement from its central position, theinformation is sent to the processor.


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MICR

Magnetic Ink Character Recognition, or MICR, is a special

kind of character recognition technology that was adoptedmainly by the banking industry to facilitate the processingof cheques.

A special ink called magnetic ink is used to write thecharacter of the cheques and deposit forms which are to beprocessed by an MICR.

The magnetic ink is magnetized during the input process.

The MICR reads these pattern and compared with thespecial pattern stored in the memory


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OMR (Optical Mark Reader) Special marks such as square or bubble are prepared onexamination answer sheets.

The user fill in theses squares or bubbles with soft pencil or

ink to indicate there choices. These squares are detected by

an OMR and the corresponding signals are sent to the

processor.

If a mark is present, it reduces the amount of reflected light .

If a mark is not present the amount of light reflected is not

reduced.


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Smart Card Reader

Smart cards stores data in the magnetic stripes which is

present at the back side of the card. These data cannot be read visually, and therefore, to read

this data, special card reader machine is required, whichcan decode data present on thesemagnetic strips.

The smart card can hold many information and it is

impossible to duplicate it because data is stored inmagnetic strips.

There is a , Contact Smart Cards which has a small goldchip about inch in diameter on the front. When insertedinto a reader, the chip makes contact with electrical

connectors that can read inform

ation from

the chip andwrite information back. The cards do not contain anybatteries, energy is supplied by the card reader. Contactsmart card readers are used as a communications mediumbetween the smart card and a host, e.g. a computer.


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Digitizer Digitization, is the process of turning an

analog signal into a digital

representation of that signal.

An example of digitizer is GraphicTablet


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ScannerTypes Of Scanner

Drum scanners

Flatbed scanner

H

and scanner


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Output Devices

The output devices receive information from the

computer and provide them to user in a readable format.

The computer sends information to the output devices in

binary coded forms. Then, output devices convert themin to a form, which can be used by user. Some output

devices are

Printer

Monitor

Plotter

Speaker


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Printer

It is a device that produces a hard copy which is

permanent human-readable text of documents storedin electronic form, usually on physical print media

such as paper or transparencies.

The data received by a printer may be:

a string of characters

a bitmapped image

a vector image

Printers which are used with computer can beclassified in two ways.

Line Printer

Character Printer


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In chain printers which is also known as train printers, thecharacter set is arranged multiple times around a chain thattravels horizontally past the print line. In either case, to print aline, precisely timed hammers strike against the back of the paperat the exact moment that the correct character to be printed is

passing in front of the paper. The paper presses forward against aribbon which then presses against the character form and theimpression of the character form is printed onto the paper.

A

AAAAAAAAAAA

BBBBBBBBBBBB

B

-------------------------

-------------------------

-------------------------

---------------------------------


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Inkjet Printer

It is a type of non impact printer. It is a printer thatcreates an image by spraying tiny droplets of inkfrom the printhead.

In ink-jet printer, whenever we want to print the

image the nozzel spread the ink, so there is apermanent remark on the paper. Suppose there is a 5pin then it spread the ink up to 5 pixels. But it canapproximately print up to 16 to 32 pixel at a time.

In inkjet printer the ink is stored in acartridge.A colour inkjet printer cosist of fourcartridge one each for blue, green, cyan,magenta and black.

Laser printer


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Laser printer

Laser printer are page printer. They make use of laser

beam to produce an image of the page containing text

/graphics on a photo sensitive drum.

A laser printer uses a rotating disc to reflect laser beam

onto a photosensitive drum, where the image of the page is

converted in to an electrostatic charge.


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A laser printer uses a rotating disc to reflect laser beam onto aphotosensitive drum, where the image of the page is converted into an electrostatic charge that attracts and hod the toner. A piece

of charged paper is then rolled against the drum to transfer theimage , and heat is applied to fuse the tonner and paper togetherto create the final image. In simple we can say that, the laserprinter consist of a drum coated with photoconductive materialand there is a laser beam, and the control of the laser beam is on

to the computer to turn it either on or off. When the laser beamfalls on the drum, then it produces a ve potential on it. And thegraphite powder has +ve potential, therefore both paper andpowder attracts each other. The powder is attached only wherethe electric potential is present, but the powder is also spread on

an unwanted area and it is removed by the heat. The graphitepowder is stored in the tonner. The ink is spread through thetonner and it is spread in an unsaturated form. These type ofprinter are quite, fast, clean and well suitedto the home or officeenvironment.


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VDU

A computer display is a device that can display signalsgenerated by a computer as images on a screen.

Quality factors used in monitor are:

Pixels: It is the smallest unit of monitor which is displayed

without disturbing the other point .While designning thepixels, some distance between the pixels must be there in thehorizontal as well as in vertical directin also.

Aspect Ratio: It is the ratio of the pixels in the horizontal aswell as in vertical direction also.

Resolution: No of pixels in a per unit area.

Refreshing Rate: The rate by which the pixels glow again

Refreshing Rate = 1/Refreshing Time


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VDU is categorized into

CRT

Non CRT

CRT Display


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Non CRT Display LCD

LED


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Primary Storage Devices


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1. Hard Disk

A hard disk drive is also known as hard disk, hard

drive, or the now-near-obsolete terms fixed disk,fixed drive, fixed disk drive, hard file.

It is a non-volatile, digitally encoded data storage

device that stores data on the magnetic surfaces ofhard disk platters.

It contain more than one disk or platters that is

packed together.


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Hard Disk

surface 0

surface 1

surface 2

surface 3

surface 4

surface 5

cylinderk

spindle

platter 0

platter 1

platter 2

2 RAM (R d A M )


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2. RAM (Random Access Memory) Read/write memory. DOS and application programs are loaded into RAM. Any data to be processed must be stored in memory

rather than on the hard drive. This makes accessmuch faster since the RAM can be accessed quickerthan the hard drive. When you start a program, theprogram is loaded from the hard drive into memory.

When a computer does not have enough memory,information must be swapped from RAM to the harddrive, thus slowing down performance extensively.

When application software is running in memory, anicon appears on the task bar. However, systemsoftware does not appear on the task bar.

You can purchase additional RAM chips to gain morememory for your PC. A currently acceptable amountof RAM is 512 MB/1 GB.


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3. ROM (Read-Only Memory) Contains hard coded information that is used by the operating system ROM-BIOS Video ROM Hard disk ROM ROM is a class of storage media used in computers and other electronic

devices. Because it cannot (easily) be written to, its main uses lie in thedistribution offirmware.

Modern semiconductor ROMs typically take the shape ofIC packages,i.e. "computer chips", not immediately distinguishable from other chipslike RAMs but for the text printed on the chips.

"ROM" in its strictest sense can only be read from, but all ROMs allowdata to be written into them at least once, either during initialmanufacturing or during a step called "programming".

Some ROMs can be erased and re-programmed multiple times,although they are still referred to as "read only" because thereprogramming process involves relatively infrequent, complete erasure

and reprogramming, not the frequent, bit- or word at a time updatingthat is possible with random access memory (RAM).


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Advantages

Reliability

Stores data permanently

Moderate price

Built using integrated circuits, ratherthan discrete components.

Fast: speed is between 35ns and 60ns.


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PROM

5 EPROM (E bl P bl R d O l M )


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5. EPROM (Erasable Programmable Read-Only Memory)

EPROM is a type of computer memory chip thatretains its data when its power supply is switched off.

In other words, it is non-volatile. It is an array offloating gate transistors individually programmed byan electronic device that supplies higher voltagesthan those normally used in electronic circuits.

Once programmed, an EPROM can be erased only by

exposing it to strong ultravioletlight. That UV lighthas usually a wavelength of 235nm (for optimumerasure time) and belongs to the UVC range of UVlight.

EPROMs are easily recognizable by the transparent

quartz window in the top of the package, throughwhich the silicon chip can be seen, and which permitsUV light during erasing.

6 EEPROM (Electronically Erasable Programmable Read Only Memory)


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6. EEPROM (Electronically Erasable Programmable Read-Only Memory)

EEPROM is a non-volatile storage chip used in computers andother devices to store small amounts of volatile data.

When larger amounts of more static data are to be stored othermemory types like flash memory are more economical. EEPROMs come in a range of capacities from a few bytes to

over 128 kilobytes and are typically used to store configurationparameters, and in modern computers they replace the hithertocommon CMOS nonvolatile BIOS memory.

For example, in personal computers these chips are used tostore the BIOS code and related system settings. While RAM has no limitations on rewrites to memory, EEPROMs

are limited in that repeated write and erase cycles eventuallydamage the thin insulating layer, a process called wear out.

RAM is generally much faster to write than EEPROM (typically afew nanoseconds as opposed to a few microseconds), and most

types ofRAM are volatile (they lose their contents when poweris removed).

EEPROM retains its data after power down.


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8 SRAM (Static Random Access Memory)


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8. SRAM (Static Random Access Memory)

SRAM is a type ofsemiconductor memory. The word "static" indicates that the memory retains

its contents as long as power remains applied, unlikedynamic RAM (DRAM) that needs to be periodicallyrefreshed.

Each bitin an SRAM is stored on four transistors thatform two cross-coupled inverters.

This storage cell has two stable states which areused to denote 0 and 1.

Two additional access transistors serve to control theaccess to a storage cell during read and writeoperations.

It thus typically takes six MOSFETs to store onememory bit. The size of an SRAM with m address lines and n data

lines is 2m words, or bits.

9 DDRAM(Double Density RAM )


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9. DDRAM(Double Density RAM )

Double Data Rate SDRAM (DDR) doubles transfer rates bytransferring data on both the rising and falling edges of the

clock. DDR uses additional power and ground lines and is packaged on

a 184-pin DIMM module rather than the 168-pin DIMM used bythe first SDRAM chips.

DDR2 chips increase data rates using various techniques suchas on-die termination, which places the terminating transistorsthat eliminate excess signal noise on the chip itself.

DDR2 modules require 240-pin DIMM slots, and although theyare the same length as DDR, they are keyed differently and willnot fit into the DDR slot.

A CPU cache is a cache used by the central processing unitofa computer to reduce the average time to access memory.

The cache is a smaller, faster memory which stores copies of

the data from the most frequently used main memory locations.


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Secondary Storage Devices

CD drive


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CD-ROM (Compact Disc Read-Only Memory) is acompact disc that contains data accessible by a computer.

While the compact disc format was originally designed formusic storage and playback, the format was later adapted tohold any form of binary data.

CD-ROMs are popularly used to distribute computersoftware, including games and multimedia applications,though any data can be stored (up to the capacity limit of adisc).

Some CDs hold both computer data and audio with thelatter capable of being played on a CD player, whilst data

(such as software or digital video) is only usable on acomputer. These are called Enhanced CDs.

CD-ROM discs are identical in appearance to audio CDs,and data is stored and retrieved in a very similar manner(only differing from audio CDs in the standards used to

store the data).

CD drive


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CD drive

Discs are made from a 1.2 mm thick disc ofpolycarbonate plastic, with a thin layer of aluminium tomake a reflective surface.

The most common size of CD-ROM disc is 120 mm indiameter, though the smaller Mini CD standard with an80 mm diameter, as well as numerous non-standard sizes

and shapes (e.g. business card-sized media) are alsoavailable.

Data is stored on the disc as a series of microscopicindentations ("pits", with the gaps between them referredto as "lands").

A laser is shone onto the reflective surface of the disc toread the pattern of pits and lands.

Cd drive


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Cd drive

Because the depth of the pits is

approximately one-quarter to one-sixth ofthe wavelength of the laser light used toread the disc, the reflected beam's phase isshifted in relation to the incoming beam,

causing destructive interference andreducing the reflected beam's intensity.

This pattern of changing intensity of the

reflected beam is converted into binary data.


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Secondary Storage Devices

Sequential Access Devices Direct Access Devices

Magnetic Tape Magnetic Disk Optical Disk

CD-ROM Worm DiskFloppy Disk


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Sequential File Organization

In this records are stored and accessed one

after another.

Magnetic Tape is a storage medium that issequential in nature.

Record Record Record Record

1 2 3 4


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Direct File Access.

In this record is directly read from adisk without reading all preceding

records. The order of storage of records is

immaterial.

It is the fastest of the three accessmethods


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Indexed Sequential Access File It is one of the most common technique

for accessing disk records directly.

During the creation of records an indexis provided to the record using the filehandling mechanism.

The index indicates the location of eachrecord and where a particular recordcan be found.

History Of Computer-1

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