INTRODUCTION TO HARDWARE

ICS-XI-HBISE COMPUTER SCIENCE
SYEDA FARZANA SHAH (BS-IT, MBA-HRM) 1
Chapter #2
INTRODUCTION TO HARDWARE
Computer – Hardware
Hardware represents the physical and tangible components of a computer, i.e. the components
that can be seen and touched.
Examples of Hardware are the following −
 Input devices − keyboard, mouse, etc.
 Output devices − printer, monitor, etc.
 Secondary storage devices − Hard disk, CD, DVD, etc.
 Internal components − RAM,CPU, motherboard, etc.
INPUT AND OUTPUT DEVICES OF COMPUTER
Input Devices
A device that can be used to insert data into a computer system is called as input device.
It allows people to supply information to computers without any input devices, a computer would
only be a display device and not allow users to interact with it,
Examples of input devices include keyboards, mouse, scanners, digital cameras and Light pen,
joysticks, Touch-screen, OMR, OBR,OCR.
Keyboard
Most common and very popular input device is keyboard. The keyboard helps in inputting the
data to the computer. The layout of the keyboard is like that of traditional typewriter, although
there are some additional keys provided for performing some additional functions.
Keyboard is of two sizes 84 keys or 101/102 keys, but now 104 keys or 108 keys keyboard is also
available for Windows and Internet.
Mouse
Mouse is most popular Pointing device. It is a very famous cursor-control device. It is a small palm
size box with a round ball at its base which senses the movement of mouse and sends
corresponding signals to CPU on pressing the buttons.
Generally it has two buttons called left and right button and scroll bar is present at the mid.
Mouse can be used to control the position of cursor on screen, but it cannot be used to enter
text into the computer.
Advantages

 EASY to use
 Not very expensive
 Moves the cursor faster than the arrow keys of keyboard.
Joystick
Joystick is also a pointing device which is used to move cursor position on a monitor screen. It is
a stick having a spherical ball at its both lower and upper ends. The lower spherical ball moves in
a socket. The Joystick can be moved in all four directions.
The function of joystick is similar to that of a mouse. It is mainly used in Computer Aided
Designing (CAD) and playing computer games.
Touchpad
Also called a glide pad, glide point, pressure sensitive tablet, or trackpad, a touchpad is an input
device on laptops and some keyboards. It allows the user to move a cursor with their finger. It
can be used in place of an external mouse. A touchpad is operated by using your finger and
dragging it across the flat surface of the touchpad.
Touch screen
Touch screen is a input device. Touch screen technology is the direct manipulation type gesture
based technology. Direct manipulation is the ability to manipulate digital world inside a screen
without the use of command-line-commands. A device which works on touch screen technology
is coined as Touch screen. A touch screen is an electronic visual display capable of ‘detecting’ and
effectively ‘locating’ a touch over its display area.
It is sensitive to the touch of a human finger, hand, pointed finger nail and passive objects like
stylus. Users can simply move things on the screen, scroll them, make them bigger and many
more.
Light Pen
Light pen is a pointing device which is similar to a pen. It is used to select a displayed menu item
or draw pictures on the monitor screen. It consists of a photocell and an optical system placed in
a small tube.
When light pen’s tip is moved over the monitor screen and pen button is pressed, its photocell
sensing element detects the screen location and sends the corresponding signal to the CPU.
Scanner (image Scanner)
Scanner is an input device which works more like a photocopy machine. It is used when some
information is available on a paper and it is to be transferred to the hard disc of the computer for
further manipulation.
Scanner captures images from the source which are then converted into the digital form that can
be stored on the disc. These images can be edited before they are printed.
General types of Scanners:
 Hand-held Scanners are hand held devices that scan an image or document by passing
over it. They are small, portable and cheap.

 Flatbed Scanners are the most common type of desktop scanners. When a document or
object is to be scanned, it is placed face down on the glass surface of the scanner. The
scanning head and light source under the glass automatically move down the document
at a constant speed.
 Feed-in (or sheet-fed) Scanners work differently from flatbed scanners in that the
scanning components remain stationary. In this instance, the page being scanned is
moved past the scanning head rather than the other way around. Feed-in or sheet-fed
scanners work very well in conjunction with document feeders and are suitable for
scanning multiple page documents automatically.
Character/mark Recognizers:
Optical Character Reader (OCR)
OCR is an input device used to read a printed text. OCR scans text optically character by character,
converts them into a machine readable code and stores the text on the system memory.
Bar Code Readers
Bar Code Reader is a device used for reading bar coded data (data in form of light and dark lines).
Bar coded data is generally used in labelling goods, numbering the books etc. It may be a hand
held scanner or may be embedded in a stationary scanner.
Bar Code Reader scans a bar code image, converts it into an alphanumeric value which is then
fed to the computer to which bar code reader is connected.
Magnetic Ink Card Reader (MICR)
MICR input device is generally used in banks because of a large number of cheques to be
processed every day. The bank’s code number and cheque number are printed on the cheques
with a special type of ink that contains particles of magnetic material that are machine readable.
This reading process is called Magnetic Ink Character Recognition (MICR). The main advantage of
MICR is that it is fast and less error prone.
Optical Mark Reader (OMR)
OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil.
It is used where one out of a few alternatives is to be selected and marked. It is specially used for
checking the answer sheets of examinations having multiple choice questions.
Output Devices
A device which is used to display result from a computer is called as output device.
It Allows people to receive information from computers. An output device is any peripheral that
receives or displays output from a computer. The picture shows an inkjet printer, an output
device that can make a hard copy of anything being displayed on a monitor. Output device is

electronic equipment connected to a computer and used to transfer data out of the computer in
the form of text, images, sounds or print.
Examples of output devices include : Plotters, LCD, Plasma Display, Printers, etc.
Monitors
Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a
computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form.
The sharpness of the image depends upon the number of pixels.
Characteristics of Monitor:
- Screen size – the viewing area is measured diagonally; in other words, a 17'' screen measures
17 inches from top left corner to the bottom right.
- Resolution – the clarity of the image depends on the number of pixels (short picture elements)
contained on a display, horizontally and vertically. A typical resolution is 1024 x768.
- Brightness – the luminance of images is measured in cd/m² (candela per square meter).
- Color depth – the number of colors a monitor can display. For example, a VGA monitor produces
256 colors, enough for home users; a SuperVGA can produce up to 16.7 million colors, so is ideal
for photographic work and video games.
- Refresh rate – the number of times that the image is drawn each second. If a monitor has a
refresh rate of 75 Hz, it means that the screen is scanned 75 times per second. If the rate is low,
you will notice a flicker, which can cause eye fatigue.
There are two kinds of viewing screen used for monitors.
 Cathode-Ray Tube (CRT)
 Flat-Panel Display
Cathode-Ray Tube (CRT) Monitor
The CRT display is made up of small picture elements called pixels. The smaller the pixels, the
better the image clarity or resolution. It takes more than one illuminated pixel to form a whole
character, such as the letter ‘e’ in the word help.
A finite number of characters can be displayed on a screen at once. The screen can be divided
into a series of character boxes - fixed location on the screen where a standard character can be
placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines
vertically.
There are some disadvantages of CRT −
 Large in Size
 High power consumption
Flat-Panel Display Monitor
The flat-panel display refers to a class of video devices that have reduced volume, weight and
power requirement in comparison to the CRT. You can hang them on walls or wear them on
your wrists. Current uses of flat-panel displays include calculators, video games, monitors,
laptop computer, and graphics display.
The flat-panel display is divided into two categories −
 Emissive Displays − Emissive displays are devices that convert electrical energy into light.
For example, plasma panel and LED (Light-Emitting Diodes).

 Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or
light from some other source into graphics patterns. For example, LCD (Liquid-Crystal
Device).
Printers
Printer is the most important output device, which is used to print information on paper.
There are two types of printers
 Impact Printers
 Non-Impact Printers
Impact Printers
The printers that print the characters by striking against the ribbon and onto the paper are called
impact printers.
Characteristics of Impact Printers are following
 Very low consumable costs
 Impact printers are very noisy
 Useful for bulk printing due to low cost
 There is physical contact with the paper to produce an image
These printers are of two types
 Character printers
 Line printers
Character Printers:
Character Printers are printers which print one character at a time.
These are of further two types
 Dot Matrix Printer(DMP)
 Daisy Wheel
Dot Matrix Printer
In the market one of the most popular printer is Dot Matrix Printer because of their ease of
printing features and economical price. Each character printed is in form of pattern of Dot’s and
head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which comes out to form a
character that is why it is called Dot Matrix Printer.
Advantages
 Inexpensive
 Widely Used
 Other language characters can be printed
Disadvantages
 Slow Speed

 Poor Quality
Line Printers
Line printers are printers which print one line at a time.
These are of further two types
 Drum Printer
 Chain Printer
Drum Printer
This printer is like a drum in shape so it called drum printer. The surface of drum is divided into
number of tracks. Total tracks are equal to size of paper i.e for a paper width of 132 characters,
Drum will have 132 tracks. A character set is embossed on track.
Advantages
 Very high speed
Disadvantages
 Very expensive
 Characters fonts cannot be changed
Chain Printer
In this printer chain of character sets are used so it called Chain Printers. A standard character
set may have 48, 64, 96 characters.
Advantages
 Character fonts can easily be changed.
 Different languages can be used with the same printer.
Disadvantages
 Noisy
 Do not have the ability to print any shape of characters.
Non-impact Printers
The printers that print the characters without striking against the ribbon and onto the paper, are
called Non-impact Printers. These printers print a complete page at a time, also called as Page
Printers.
These printers are of two types
 Laser Printers
 Inkjet Printers
Characteristics of Non-impact Printers
 Faster than impact printers.
 High quality.
 Support many fonts and different character size.

Laser Printers
These are non-impact page printers. They use laser lights to produces the dots needed to form
the characters to be printed on a page.
Advantages
 Very high speed.
 Very high quality output.
 Give good graphics quality.
 Support many fonts and different character size.
Disadvantage
 Cannot be used to produce multiple copies of a document in a single printing.
Inkjet Printers
Inkjet printers are non-impact character printers based on a relatively new technology. They print
characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output
with presentable features.
Plotters
A plotter is a special output device used to produce hard copies of large graphs and designs on
paper, such as construction maps, engineering drawings, architectural plans and business charts.
The plotter is either a peripheral component that you add to your computer system or a
standalone device with its own internal processor.
Drum Plotter
A drum plotter is a pen plotter that wraps the paper around a drum with a pin feed attachment.
The drum then rotates the paper as pens move across it and draw the image. It was the first
output device used to print graphics and large engineering drawings.
Flat-Bed Plotter
A flat-bed plotter is a mechanical drafting device used with many CAD programs for designers.
The paper remains stationary on a flat surface while a pen moves across it horizontally and
vertically. This plotter may use several different pen colors to create the graphics. The size of the
graphic is limited to the size of the flat-bed plotter's surface.
Computer - CPU (Central Processing Unit)
Central Processing Unit (CPU) consists of the following features −
 CPU is considered as the brain of the computer.

 CPU performs all types of data processing operations.
 It stores data, intermediate results, and instructions (program).
 It controls the operation of all parts of the computer.
CPU itself has following three components.
 Memory or Storage Unit
 Control Unit
 ALU(Arithmetic Logic Unit)
Memory or Storage Unit
This unit can store instructions, data, and intermediate results. This unit supplies information to
other units of the computer when needed. It is also known as internal storage unit or the main
memory or the primary storage or Random Access Memory (RAM).
Its size affects speed, power, and capability. Primary memory and secondary memory are two
types of memories in the computer. Functions of the memory unit are −
 It stores all the data and the instructions required for processing.
 It stores intermediate results of processing.
 It stores the final results of processing before these results are released to an output
device.
 All inputs and outputs are transmitted through the main memory.

Control Unit
This unit controls the operations of all parts of the computer but does not carry out any actual
data processing operations.
Functions of this unit are −
 It is responsible for controlling the transfer of data and instructions among other units of
a computer.
 It manages and coordinates all the units of the computer.
 It obtains the instructions from the memory, interprets them, and directs the operation
of the computer.

 It communicates with Input/output devices for transfer of data or results from storage.
 It does not process or store data.
ALU (Arithmetic Logic Unit)
This unit consists of two subsections namely,
 Arithmetic Section
 Logic Section
Arithmetic Section: Function of arithmetic section is to perform arithmetic operations like
addition, subtraction, multiplication, and division. All complex operations are done by making
repetitive use of the above operations.
Logic Section: Function of logic section is to perform logic operations such as comparing,
selecting, matching, and merging of data.
COMPUTER MEMORY
MAIN MEMORY
A Main memory, also called primary or internal memory is the part of the computer system that
holds data and instructions for processing. It is mainly used to store data that is used by the
system at startup and to run various types of programs such as the operating system and other
programs. Typically, Main memory is contained on microchips that are either attached or
connected to the computer's motherboard. Computer memory can range from a couple of
megabytes (MBs) to several gigabytes (GBs). When users load software from a storage medium,
it is first loaded in the main memory and then executed or processed.
Types of Main Memory
Main memory is divided into the following three types.

 Internal Processor Memory
 RAM
 ROM
Internal Processor Memory
These memories are directly accessible to the CPU. Cache memory and processor registers are
the examples of such memories. These are extremely fast memories.
Processor Registers
Registers are small memory units. There are a large number of registers inside the processor.
There function is to temporarily store binary information and pass it on to the other parts of the
processor or main memory during the execution of program instructions. Some commonly used
registers inside the microprocessors are accumulator, instruction register, data register, program
counter and memory address register.
Cache Memory
Cache memory is a very high speed semiconductor memory which can speed up the CPU. It acts
as a buffer between the CPU and the main memory. It is used to hold those parts of data and
program which are most frequently used by the CPU. The parts of data and programs are
transferred from the disk to cache memory by the operating system, from where the CPU can
access them.
Advantages
The advantages of cache memory are as follows −
 Cache memory is faster than main memory.
 It consumes less access time as compared to main memory.
 It stores the program that can be executed within a short period of time.
 It stores data for temporary use.
Disadvantages
The disadvantages of cache memory are as follows −
 Cache memory has limited capacity.
 It is very expensive.
RAM (Random Access Memory) is the internal memory of the CPU for storing data,
program, and program result. It is a read/write memory which stores data until the machine is
working. As soon as the machine is switched off, data is erased.
Access time in RAM is independent of the address, that is, each storage location inside the
memory is as easy to reach as other locations and takes the same amount of time. Data in the
RAM can be accessed randomly but it is very expensive.
RAM is volatile, i.e. data stored in it is lost when we switch off the computer or if there is a power
failure. Hence, a backup Uninterruptible Power System (UPS) is often used with computers. RAM
is small, both in terms of its physical size and in the amount of data it can hold.

RAM is of two types −
 Static RAM (SRAM)
 Dynamic RAM (DRAM)
Static RAM (SRAM)
The word static indicates that the memory retains its contents as long as power is being
supplied. However, data is lost when the power gets down due to volatile nature. SRAM chips
use a matrix of 6-transistors and no capacitors. Transistors do not require power to prevent
leakage, so SRAM need not be refreshed on a regular basis.
There is extra space in the matrix, hence SRAM uses more chips than DRAM for the same amount
of storage space, making the manufacturing costs higher. SRAM is thus used as cache memory
and has very fast access.
Characteristic of Static RAM
 Long life
 No need to refresh
 Faster
 Used as cache memory
 Large size
 Expensive
 High power consumption
Dynamic RAM (DRAM)
DRAM, unlike SRAM, must be continually refreshed in order to maintain the data. This is done
by placing the memory on a refresh circuit that rewrites the data several hundred times per
second. DRAM is used for most system memory as it is cheap and small. All DRAMs are made up
of memory cells, which are composed of one capacitor and one transistor.
Characteristics of Dynamic RAM
 Short data lifetime
 Needs to be refreshed continuously
 Slower as compared to SRAM
 Used as RAM
 Smaller in size
 Less expensive
 Less power consumption
ROM:READ ONLY MEMORY
ROM stands for Read Only Memory. The memory from which we can only read but cannot write
on it. This type of memory is non-volatile. The information is stored permanently in such
memories during manufacture. A ROM stores such instructions that are required to start a
computer. This operation is referred to as bootstrap. ROM chips are not only used in the
computer but also in other electronic items like washing machine and microwave oven.

Various types of ROMS and their characteristics.
PROM (Programmable Read Only Memory)
PROM is read-only memory that can be modified only once by a user. The user buys a blank
PROM and enters the desired contents using a PROM program. Inside the PROM chip, there are
small fuses which are burnt open during programming. It can be programmed only once and is
not erasable.
EPROM (Erasable and Programmable Read Only Memory)
EPROM can be erased by exposing it to ultra-violet light for a duration of up to 40 minutes.
Usually, an EPROM eraser achieves this function. During programming, an electrical charge is
trapped in an insulated gate region. The charge is retained for more than 10 years because the
charge has no leakage path. For erasing this charge, ultra-violet light is passed through a quartz
crystal window (lid). This exposure to ultra-violet light dissipates the charge. During normal use,
the quartz lid is sealed with a sticker.
EEPROM (Electrically Erasable and Programmable Read Only Memory)
EEPROM is programmed and erased electrically. It can be erased and reprogrammed about ten
thousand times. Both erasing and programming take about 4 to 10 ms (millisecond). In EEPROM,
any location can be selectively erased and programmed. EEPROMs can be erased one byte at a
time, rather than erasing the entire chip. Hence, the process of reprogramming is flexible but
slow.
Advantages of ROM
The advantages of ROM are as follows −
 Non-volatile in nature
 Cannot be accidentally changed
 Cheaper than RAMs
 Easy to test
 More reliable than RAMs
 Static and do not require refreshing
 Contents are always known and can be verified
Difference between Main Memory and Secondary Storage:
Primary Memory (Main Memory)
Primary memory holds only those data and instructions on which the computer is currently
working. It has a limited capacity and data is lost when power is switched off. It is generally made
up of semiconductor device. These memories are not as fast as registers. The data and
instruction required to be processed resides in the main memory. It is divided into two
subcategories RAM and ROM.

Characteristics of Main Memory
 These are semiconductor memories.
 It is known as the main memory.
 Usually volatile memory.
 Data is lost in case power is switched off.
 It is the working memory of the computer.
 Faster than secondary memories.
 A computer cannot run without the primary memory.
Secondary Memory
This type of memory is also known as external memory or non-volatile. It is slower than the main
memory. These are used for storing data/information permanently. CPU directly does not access
these memories, instead they are accessed via input-output routines. The contents of secondary
memories are first transferred to the main memory, and then the CPU can access it. For
example, disk, CD-ROM, DVD, etc.
Characteristics of Secondary Memory
 These are magnetic and optical memories.
 It is known as the backup memory.
 It is a non-volatile memory.
 Data is permanently stored even if power is switched off.
 It is used for storage of data in a computer.
 Computer may run without the secondary memory.
 Slower than primary memories.
Computer - Memory Units
Memory unit is the amount of data that can be stored in the storage unit. This storage capacity
is expressed in terms of Bytes.
The following table explains the main memory storage units −
S.No. Unit & Description
1
Bit (Binary Digit)
A binary digit is logical 0 and 1 representing a passive or an active state of a component in an
electric circuit.
2
Nibble
A group of 4 bits is called nibble.
3
Byte
A group of 8 bits is called byte. A byte is the smallest unit, which can represent a data item or
a character.

4
Word
A computer word, like a byte, is a group of fixed number of bits processed as a unit, which
varies from computer to computer but is fixed for each computer.
The length of a computer word is called word-size or word length. It may be as small as 8 bits
or may be as long as 96 bits. A computer stores the information in the form of computer
words.
The following table lists some higher storage units –
Table 2.1 Memory Units and their Equivalents
Memory characteristics
The important characteristics of any memory device are its access mode, access time, transfer
rate, capacity and cost.
 Access mode: Memory has two major access modes, Sequential and Random. In
Sequential access mode memory can be accessed only in serial order i.e. if we have to
access 4th memory location then we first would have to move to first three locations and
skip them and only then we can access the 4th location. It is also called serial access mode.
In Random access mode memory location can be accessed at random i.e. if we have to
access 4th location then we can directly go to 4th location and access it. It is also called
direct access mode.
 Access time: It is the time taken to retrieve data from memory. Access time in sequential
access memory devices is more than the random access memory devices.
 Data transfer rate: It is the time taken to transfer data from one memory device to the
other. For example time taken to transfer data for Hard disk to the main memory (RAM).
 Capacity: The memory capacity is the amount of space that a memory device has to store
data or the amount of memory required for a program to run.
 Cost: It is the price that computer users have to pay as per capacity of the memory device.

SECONDARY MEMORY
Secondary memory is also known as backing storage, auxiliary storage or mass storage. It stores
large amount of information permanently. Some examples of secondary storage devices are Hard
Disk drive, CD, DVD, Blue Ray Disk, Flash memory and Memory cards.
SEQUENTIAL ACCESS AND DIRECT ACCESS MEMORY DEVICES
Memory devices are classified into sequential access memory and direct access memory devices,
based on the access mode.
Sequential Access Memory
It is a type of memory in which data is accessed sequentially one after the other. A particular
stored data is found by sequencing through all locations until the desired data is reached. This
produces access times, which are much longer than those of direct access memories. Examples
of sequential access memory devices include magnetic tapes and audio/video tapes.
Direct Access Memory
In this type of memory the data is accessed directly or randomly. Semiconductor memories, disk
memories and optical memories are direct access memories. Direct access memory is also known
as random access memory. Hard disk, compact disk and flash memory are examples of direct
access memory.
TYPES OF SECONDARY STORAGE DEVICES
Secondary storage devices are classified into the following types.
 Magnetic Tape
 Magnetic Disks
 Optical Disks
 Chip Memory
Magnetic Tape
Magnetic tape is a plastic strip with a magnetic coated material. Bits are recorded as magnetic
spots on the tape along several tracks. Usually 7 or 9 bits are recorded simultaneously to form a
character. Read/write heads are mounted one in each track so that data can be recorded and
read as a sequence of characters. Magnetic tape is either in the form of cassette or big reels.
Advantages
 It is a cheap storage device
 Tapes are used for storing large amount of data
 Modern tapes can store data up to 5 TB.
 It is used with minicomputers and mainframes for backups and archives.
Disadvantages
Magnetic tape is slow in operation as it has sequential access to data.

Magnetic Disks (Floppy Disk)
A magnetic disk is a flat disk coated with a magnetic material on which data/information
is stored in digital form. Data/Information is stored in digital form in the shape of tiny magnetized
spots called bits. Hard disk is the common type of magnetic disk in use today. Some other types
of magnetic disks were also used in the past like Floppy disks and Zip disks. These disks are
obsolete and not in use now days. These disks have been replaced by optical disks and USB flash
drives which are more reliable and have more storage capacity.
The only magnetic disk used now days is the Hard disk.
Hard Disk
Hard disk contains one or many platters (disks) coated with magnetic material on both sides. The
platters are attached to a spindle holding them in parallel with equal gap. All the platters rotate
together at high speed. Bits are stored on the magnetic surface in spots along concentric circles
called tracks. Hard disks contain thousands of tracks. Track is divided into sections called sectors.
Each platter has two read/write heads for writing data to and reading data from both surfaces of
the platter. The storage capacity of modern hard disks is in Tera bytes.
Optical Disks
Optical disk is a plastic-coated disk that can store digital data. Data is stored in optical disk in
digital form by laser technology as tiny bumps etched on the surface.
The following are types of optical disks.
 CDs
 DVDs
 Blu-ray Disk
 FLASH MEMORY/CHIP MEMORY
Compact Disks (CDs)
It is an optical disk used for storing digital data. It was originally developed for storing and
playback of sound recording but later on its use expanded to computer data storage. A CD is 1.2
millimeters thick with a diameter of 120 millimeters. It is made up of polycarbonate plastic and
weighs 15 to 20 grams. The storage capacity of CDs ranges from 350 MB to 800MB. CDs are
popular for storing data, application programs, device drivers, Windows operating system,
images and videos. A CD has a single spiral track that spirals from the center to the outside edge.
Information is stored on a CD in the form of lands and bumps. A binary 0 is represented by a
bump and a 1 by a land.
Working of CD drive:
A CD drive/player is used for reading the data stored on the CD. The job of CD player is to focus
the laser on the track of bumps. The laser beam passes through the polycarbonate layer, reflects
off the aluminium layer and hits the censor that detects changes in light. The bump scatters the
light and the land reflects it into the censor. The change in reflectivity is transmitted as 0s and 1s
into the memory of the computer.

Digital Video/Versatile Disks (DVDs)
DVD is very similar to CD but has larger data storage capacity. Its data storage capacity is about
seven times more than CD. It has replaced the video tapes that were used in the past for storing
movies. A DVD writer or player is used to read the data stored on a DVD. DVD players are
compatible with CD which means they can play CDs also.
DVDs have the same diameter and thickness as CDs. The storage capacity of DVDs ranges from
2GB to 16 GB. The MPEG (Moving Picture Experts Group) format is used for storing movies in a
compressed form on the DVDs.
Blu-ray Disk (BD)
Blu-ray is a new type of optical storage device. Its main advantage over CD and DVD is that it has
storage capacity up to 300GB and it is also faster. The bumps on the surface of Blu-ray that
represent digital information are much smaller and very densely packed compared to DVD. This
increased the storage capacity of Blu-ray. Blu-ray disks are better storage devices for storing
movies because they require a lot more storage.
Another advantage of Blu-ray disk is their durability. They have a special coating that helps
prevent scratches and marks.
FLASH MEMORY/CHIP MEMORY
Flash memory or Chip memory is a type of EEPROM. It is solid-state storage device which means
that there are no moving parts in it. Everything inside the flash or chip memory is in electronic
form. Flash memory comes in two forms, that is, in the form of flash drive and memory cards.
Flash Drive
Flash drives are also called USB flash drives. They are small and portable drives that are connected
to computers through USB ports. The storage capacity of flash memory ranges from 2GB to
256GB.
Flash Memory Cards
Memory cards are used with laptop computers and other electronic devices such as digital
cameras, mobile phones and video games. They come in various sizes and with different storage
capacity.

INTRODUCTION TO HARDWARE

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INTRODUCTION TO HARDWARE