This document provides an introduction to computer hardware. It discusses what a computer is and its basic components like input, output, processing and storage devices. It explains the differences between various types of computer memory like RAM, ROM, cache and primary memory. It also discusses concepts like Moore's Law and how computer performance and memory capacity have increased exponentially over time.

1. Introduction to Computer
Hardware
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2. Computer Hardware
• In this chapter:
• How did the computer become known as the stored-program computer?
• Do they all have the same characteristics?
• Memory on chips and memory on magnetic media, how do they differ?
• What do you look for when comparing memory devices?
• How is information moved around within the computer?
• How can you help your computer run better?
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3. What is a Computer?
• Computer
• Device capable of performing computations and making
logical decisions
• Computers process data under the control of sets of
instructions called computer programs
• Personal computers: economical enough for individual
• Distributed computing: computing distributed over networks
• Client/server computing: sharing of information across
computer networks between file servers and clients
(personal computers)
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4. What is a Computer? (cont.)
• Computer Hardware
• Various devices comprising a computer:
• Keyboard, screen, mouse, disks, memory, CD-ROM, and
processing units
• Hardware Trends: every year or two the following
approximately double (Moore’s Law):
• Amount of memory in which to execute programs
• Amount of secondary storage (such as disk storage)
• Used to hold programs and data over the longer term
• Processor speeds
• The speeds at which computers execute their programs
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5. Moore's Law
• Defined by Dr. Gordon Moore during the sixties.
• Predicts an exponential increase in component
density over time, with a doubling time of 18
months.
• Applicable to microprocessors, DRAMs , DSPs and
other microelectronics.
• Monotonic increase in density observed since the
1960s.
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6. Moore’s Law - Density
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7. Moore's Law and Performance
• The performance of computers is determined by
architecture and clock speed.
• Clock speed doubles over a 3 year period due to
the scaling laws on chip.
• Processors using identical or similar architectures
gain performance directly as a function of Moore's
Law.
• Improvements in internal architecture can yield
better gains than predicted by Moore's Law.
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8. Basic Concepts of Computer Hardware
• This model of the typical digital computer is often called the von Neumann
computer.
• Programs and data are stored in the same memory: primary
memory.
• The computer can only perform one instruction at a time.
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CPU
(Central Processing Unit)
Input
Units
Output
Units
Primary Memory

9. Basic Concepts of Computer Hardware
• Input/Output (I/O): Refers to the process of getting information into
and out of the computer.
• Input: Those parts of the computer receiving information to programs.
• Output: Those parts of the computer that provide results of computation to
the person using the computer.
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10. The Components of a Computer
• What is an input device?
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 Hardware used
to enter data
and instructions

11. The Components of a Computer
• What is an output device?
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 Hardware that
conveys
information
to a user

12. Sources of Data
for the Computer
• Two types of data stored within a computer:
• Original data or information: Data being introduced to a computing
system for the first time.
• Computers can deal directly with printed text, pictures, sound, and other common
types of information.
• Previously stored data or information: Data that has already been
processed by a computer and is being stored for later use.
• These are forms of binary data useful only to the computer.
• Examples: Floppy disks, DVD disks, and music CDs.
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13. Computer Components
• Input/Output (Mouse, Keyboard, Display)
• Processor and Memory
• Storage
• Multimedia( Audio, Graphics and Video Support)
• Connection and Expansion
• Battery and Power
• Communication
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14. Introduction to memory and memory units
• In order to save data and instructions, memory is required. Memory is
divided into cells, and they are stored in the storage space present in
the computer. Every cell has its unique location/address. Memory is
very essential for a computer as this is the way it becomes somewhat
more similar to a human brain.
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16. Storage Devices or Computer Memory
In computing, memory refers to the physical devices used to store
programs (sequences of instructions) or data (e.g. program state
information) on a temporary or permanent basis for use in a computer
or other digital electronic device. The term primary memory is used for
the information in physical systems which are fast (i.e. RAM), as a
distinction from secondary memory, which are physical devices for
program and data storage which are slow to access but offer higher
memory capacity. Primary memory stored on secondary memory is
called "virtual memory".
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17. CPU Register
• In computer architecture, a processor register is a small amount of
storage available as part of a digital processor, such as a central
processing unit (CPU). Such registers are typically addressed by
mechanisms other than main memory and can be accessed faster.
Almost all computers, load-store architecture or not, load data from a
larger memory into registers where it is used for arithmetic,
manipulated or tested by machine instructions. Manipulated data is
then often stored back into main memory, either by the same
instruction or a subsequent one. Modern processors use either static
or dynamic RAM as main memory, with the latter usually accessed via
one or more cache levels.
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18. Cache Memory
• In computer engineering, a cache is a component that transparently
stores data so that future re quests for that data can be served faster.
The data that is stored within a cache might be values that have been
computed earlier or duplicates of original values that are stored
elsewhere. If requested data is contained in the cache (cache hit), this
requ est can be served by simply reading the cache, which is
comparatively faster. Otherwise (cache miss), the data has to be
recomputed or fetched from its original storage location, which is
comparatively slower. Hence, the greater the number of requests that
can be served from the cache, the faster the overall system
performance becomes.
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19. Type od Cache
• Cache (L1) The Level 1 cache, or primary cache, is on the CPU and is used for temporary
storage of instructions and data organized in blocks of 32 bytes. Primary cache is the
fastest form of storage. Because it's built in to the chip with a zero wait-state (delay)
interface to the processor's execution unit, it is limited in size. For all L1 cache designs
the control logic of the primary cache keeps the most frequently used data and code in
the cache and updates external memory only when the CPU hands over control to other
bus masters, or during direct memory access by peripherals.
• Cache (L2) Most PCs are offered with a Level 2 cache to bridge the processor/memory
performance gap. Level 2 cache - also referred to as secondary cache) uses the same
control logic as Level 1 cache. The aim of the Level 2 cache is to supply stored
information to the processor without any delay (wait-state). For this purpose, the bus
interface of the processor has a special transfer protocol called burst mode. A burst cycle
consists of four data transfers where only the address of the first 64 is output on the
address bus. The most common Level 2 cache is synchronous pipeline burst
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20. Primary Memory
• Primary memory (or main memory or internal memory), often
referred to simply as memory, is the only one directly accessible to
the CPU. The CPU continuously reads instructions stored there and
executes them as required. Any data actively operated on is also
stored there in uniform manner. It can be divided into two essential
types: RAM and ROM
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21. • RAM (random access memory) is the place in a computer where the
operating system, application programs, and data in current use are kept so
that they can be quickly reached by the computer's processor. RAM is
much faster to read from and write to than the other kinds of storage in a
computer, the hard disk, floppy disk, and CD- ROM. However, the data in
RAM stays there only as long as your computer is running. When you turn
the computer off, RAM loses its data. When you turn your computer on
again, your operating system and other files are once again loaded into
RAM, usually from your hard disk. There are two different types of RAM:
• DRAM (Dynamic Random Access Memory)
• SRAM (Static Random Access Memory)
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22. DRAM
• DRAM (Dynamic Random Access Memory) Dynamic RAM is a type of
RAM that only holds its data if it is continuously accessed by special
logic called a refresh circuit. Many hundreds of times each second,
this circuitry reads the contents of each memory cell, whether the
memory cell is being used at that time by the computer or not. Due
to the way in which the cells are constructed, the reading action itself
refreshes the contents of the memory. If this is not done regularly,
then the DRAM will lose its contents, even if it continues to have
power supplied to it. This refreshing action is why the memory is
called dynamic.
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23. SRAM
• SRAM (Static Random Access Memory Static RAM is a type of RAM that
holds its data without external refresh, for as long as power is supplied to
the circuit. This is contrasted to dynamic RAM (DRAM), which must be
refreshed many times per second in order to hold its data contents. SRAMs
are used for specific applications within the PC, where their strengths
outweigh their weaknesses compared to DRAM: • Simplicity: SRAMs don't
require external refresh circuitry or other work in order for them to keep
their data intact. • Speed: SRAM is faster than DRAM. In contrast, SRAMs
have the following weaknesses, compared to DRAMs: • Cost: SRAM is, byte
for byte, several times more expensive than DRAM. • Size: SRAMs take up
much more space than DRAMs (which is part of why the cost is higher).
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24. ROM
.ROM is a type of memory that normally can only be read, as opposed to RAM which can be both
read and written.
There are two main reasons that read-only memory is used for certain functions within the PC:
Permanence: The values stored in ROM are always there, whether the power is on or not. A ROM
can be removed from the PC, stored for an indefinite period of time, and then replaced, and the
data it contains will still be there. For this reason, it is called non-volatile storage.
Security: The fact that ROM cannot easily be modified provides a measure of security against
accidental (or malicious) changes to its contents. Read-only memory is most commonly used to
store system-level programs that we want to have available to the PC at all times. The most
common example is the system BIOS program, which is stored in a ROM called (amazingly enough)
the system BIOS ROM. Having this in a permanent ROM means it is available when the power is
turned on so that the PC can use it to boot up the system. Remember that when you first turn on
the PC the system memory is empty, so there has to be something for the PC to use when it starts
up.
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25. Types of Rom
• PROM- can be programmed using special equipment; it can be
written to, but only once.
• EPROM- An E PR OM is a ROM that can be erased and reprogrammed.
• EEPROM- An E PR OM is a ROM that can be erased and
reprogrammed.
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26. Secondary Memory
• Secondary memory Secondary memory (also known as external
memory or auxiliary storage or Secondary Storage), differs from
primary storage in that it is not directly accessible by the CPU. The
computer usually uses its input/output channels to access secondary
storage and transfers the desired data using intermediate area in
primary storage. Secondary storage does not lose the data when the
device is powered down—it is non-volatile. Per unit, it is typically also
two orders of magnitude less expensive than primary storage.
Consequently, modern computer systems typically have two orders of
magnitude more secondary storage than primary storage and data
are kept for a l
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27. Storage Device
• Storage Device Computer data storage, often called storage or
memory, refers to computer components and recording media that
retain digital data. Data storage is a core function and fundamental
component of computers. Storage Device Types: Magnetic Tape, Hard
Disk, Floppy Disk, Flash Memory, Optical Disk(CD,VCD,DVD), External
Storage Device
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28. Magnetic Tapes
• Magnetic tapes are used for large computers like mainframe
computers where large volume of data is stored for a longer time. In
PC also can use tapes in the form of cassettes. The storage of data in
tapes is inexpensive. Tapes consist of 34 magnetic materials that store
data permanently. It can be 12.5 mm to 25 mm wide plastic film-type
and 500 meter to 1200 meter long, which is coated with magnetic
material. The tape unit is connected to the central processor and
information is fed into or read from the tape through the processor. It
is similar to a cassette tape recorder.
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30. Magnetic Disk
• Magnetic disks used in computer are made on the circular disk and
coated with magnetic material. It rotates with very high speed inside
the computer drive. Data is stored on both the surfaces of the disk.
Magnetic disks are most popular as direct access storage device. Each
disk consists of a number of invisible concentric circles called tracks.
Information is recorded on tracks of a disk surface in the form of tiny
magnetic spots. The presence of a magnetic spot represents one bit
and its absence represents zero bit. The information stored in a disk
can be read many times without affecting the stored data. So the
reading operation is non-destructive. But if you want to write a new
data, then the existing data is erased from the disk and new data is
recorded.
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32. Floppy Disk
• It is similar to magnetic disk. It is 3.5 inch in diameter. These come in
single or double density and recorded on one or both surface of the
diskette. The capacity of a high-density 3.5 inch floppy it is 1.44
megabytes. It is cheaper than any other storage devices and is
portable. The floppy is a low cost device particularly suitable for
personal computer system.
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33. Optical Disk
• With every new application and software there is greater demand for
memory capacity. It is the necessity to store large volume of data that
has led to the development of optical disk storage medium. Optical
disks read and write the data using light. Optical disks can be divided
into the following categories:
• 1. Compact Disk/Read Only Memory (CD-ROM): CD-ROM disks are
made of reflective metals. CD-ROM is written during the process of
manufacturing by high power laser beam. Here the storage density is
very high, storage cost is very low and access time is relatively fast.
Each disk is approximately 4 A inches in diameter and can have over
600 MB of data. As the CD-ROM can be read only we cannot write or
make changes into the data contained in it.
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34. • A DVD ("digital versatile disc" or "digital video disc") is an optical disc
storage media format, invented and developed by Philips,
Sony,Toshiba, and Panasonic in 1995. DVDs offer higher storage
capacity than Compact Discs while having the same dimensions. Pre-
recorded DVDs are mass-produced using molding machines that
physically stamp data onto the DVD. Such discs are known as DVD-
ROM, because data can only be read and not written nor erased.
Blank recordable DVDs (DVD- R and DVD+R) can be recorded once
using optical disc recording technologies and supported by optical
disc drives and DVD recorder sand then function as a DVD-ROM.
Rewritable DVDs (DVD-RW, DVD+RW, and DVD-RAM) can be recorded
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35. Central Processing Unit
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37. Control Unit (CU)
• This unit controls the operations of all parts of 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.
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38. Arithmetic Logical Unit (ALU)
• 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 above
operations.
Logic Section:
Function of logic section is to perform logic operations such as comparing, selecting, matching and
merging of data.
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39. Memory Unit
• This unit can store instructions, data and intermediate results. This unit supplies information to the
other units of the computer when needed. It is also known as internal storage unit or main memory
or 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
memory unit are:
• It stores all the data and the instructions required for processing.
• It stores intermediate results of processing.
• It stores final results of processing before these results are released to an output device.
• All inputs and outputs are transmitted through main memory.
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40. Concept of Bus
• Basically, it is a means of getting data from one point to another,
point A to point B, one device to another device, or one device to
multiple devices. The bus includes not only the actual capability to
transfer data between devices, but also all appropriate signaling
information to ensure complete movement of the data from point A
to point B. To avoid loss of data, a bus must include a means of
controlling the flow of data between two devices, in order to insure
that both devices are ready to send and/or receive information.
Finally, both ends must understand the speed with which data is to be
exchanged. A bus provides for all of these elements, and it includes a
port definition to allow physical interfacing or connecting of two or
more devices.
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41. • The system bus consists of three types of buses:
• Data Bus: Carries the data that needs processing
• Address Bus: Determines where data should be sent
• Control Bus: Determines data processing
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42. Input Devices
• an input device is any peripheral (piece of computer hardware
equipment) used to provide data and control signals to an
information processing system such as a computer or other
information appliance.
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43. Mouse
• The mouse is a small device used to point to a particular place on the screen and select in order to
perform one or more actions. It can be used to select menu commands, size windows, start
programs etc. The most conventional kind of mouse has two buttons on top: the left one being used
most frequently.
Mouse Actions
• Left Click : Used to select an item.
Double Click : Used to start a program or open a file.
Right Click : Usually used to display a set of commands.
Drag and Drop : It allows you to select and move an item from one location to another. To achieve
this place the cursor over an item on the screen, click the left mouse button and while holding the
button down move the cursor to where you want to place the item, and then release it.
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44. Joystick
• The joystick is a vertical stick which moves the graphic cursor in a direction
the stick is moved. It typically has a button on top that is used to select the
option pointed by the cursor. Joystick is used as an input device primarily
used with video games, training simulators and controlling robots.
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45. Scanner
• Scanner is an input device used for direct data entry from the source
document into the computer system. It converts the document image
into digital form so that it can be fed into the computer. Capturing
information like this reduces the possibility of errors typically
experienced during large data entry. Hand-held scanners are
commonly seen in big stores to scan codes and price information for
each of the items. They are also termed the bar code readers.
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46. Light Pen
• It is a pen shaped device used to select objects on a display screen. It
is quite like the mouse (in its functionality) but uses a
• light pen to move the pointer and select any object on the screen by
pointing to the object. Users of Computer Aided Design
• (CAD) applications commonly use the light pens to directly draw on
screen.
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Digital camera
A digital camera can store many more pictures than an ordinary camera. Pictures taken using a digital
camera are stored inside its memory and can be transferred to a computer by connecting the camera to it. A
digital camera takes pictures by converting the light passing through the lens at the front into a digital
image.
The Speech Input Device
The "Microphones - Speech Recognition" is a speech Input device. To operate it we require using a
microphone to talk to the computer. Also we need to add a sound card to the computer. The Sound card
digitizes audio input into 0/1s .A speech recognition program can process the input and convert it into
machine-recognized commands or input.

48. OMR(Optical Mark Recognition)
• Many traditional OMR (Optical Mark Recognition) devices work with a
dedicated scanner device that shines a beam of light onto the form paper.
The contrasting reflectivity at predetermined positions on a page is then
utilized to detect the marked areas because they reflect less light than the
blank areas of the paper. This device is designed to be able to read
markings that have been placed in specific places on a form or card. The
person filling out the form/card will either color in a series of small squares
or perhaps make a cross within the square. The device then scans the card
and senses where marks have been placed.
• In contrast to the dedicated OMR device, desktop OMR software allows a
user to create their own forms in a word processor and print them on a
laser printer. The OMR software then works with a common desktop image
scanner with a document feeder to process the forms once filled out.
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50. BCR(bar code reader)
• A barcode reader (or barcode scanner) is an electronic device for
reading printed barcodes. Like a flatbed scanner, it consists of a light
source, a lens and a light sensor translating optical impulses into
electrical ones. Additionally, nearly all barcode readers contain
decoder circuitry analyzing the barcode's image data provided by the
sensor and sending the barcode's content to the scanner's output
port.
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51. Output Devices
• An output device is any piece of computer hardware equipment used
to communicate the results of data processing carried out by an
information processing system (such as a computer) to the outside
world. In computing, input/output, or I/O, refers to the
communication between an information processing system (such as a
computer), and the outside world. Inputs are the signals or data sent
to the system, and outputs are the signals or data sent by the system
to the outside.
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52. Monitor
• A monitor or display (also called screen or visual display unit) is an electronic
visual display for computers. The monitor comprises the display device, circuitry,
and an enclosure. The display device in modern monitors is typically a thin film
transistor liquid crystal display (TFT-LCD) thin panel, while older monitors use a
cathode ray tube about as deep as the screen size.
Different image techniques have been used for Computer monitors. Until the 21st
century most monitors were CRT but they have been phased out for LCD monitors.
Types of monitors:
1. CRT
2. Flat Panel Monitors
3,
LCD (liquid crystal display)
4, LED (light-emitting diodes) 5, plasma display panel (PDP)
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53. CRT
• creates an image on the screen using a beam of electrons.
• consists of one or more guns that fire a beam of electrons inside the
screen.
• screen is coated with very tiny Phosphor dots from inside.
• The beam of electrons repeatedly falls on the surface of screen. Every
beam fall takes only a fraction of second. CRT in color monitors
consists of three guns. These guns generate red, green and blue (RGB)
colors.
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55. Flat Panel Monitors
• Flat Panel Monitors take less space and are lightweight. These
monitors use much less power than CRTs. It does not produce
harmful radiations. It is much expensive than CRT. Notebook
computers, PDA and cellular phones use flat panel monitors. Flat
panel monitors are available in different sizes such as 15”, 17”, 18” &
19” etc. Flat panel display is made up of two plates of glass. These
plates contain a substance between them.
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56. Liquid Crystal Display
• Liquid crystal display screen contains a substance called liquid crystal.
The molecules of this substance lineup in such a way that the light
behind the screens blocked or allowed to create an image. LCDs
provide a sharper picture than CRTs and emit less radiation. LCD
displays requires less power and take up less space than CRT.
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57. LED
• LED monitors are the latest types of monitors on the market today. These
are flat panel, or slightly curved displays which make use of light-emitting
diodes for back-lighting, instead of cold cathode fluorescent
• (CCFL) back-lighting used in LCDs. LED monitors are said to use much lesser
power than CRT and LCD and are considered far more environmentally
friendly. The advantages of LED monitors are that they produce images
with higher contrast, have less negative environmental impact when
disposed, are more durable than CRT or LCD monitors, and features a very
thin design. They also don’t produce much heat while running. The only
downside is that they can be more expensive, especially for the high-end
monitors like the new curved displays that are being released.
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58. Plasma Display
• Gas plasma display uses gas plasma technology. This technology uses
a layer of gas between two glass plates. The gas release ultraviolet
light when voltage is applied. The pixels on the screen glow due to
this ultraviolet light and form an image. Plasma display is available in
the sizes of upto 150 inches wide. It provides richer colors than LCD
monitors but are more expensive. That is why, it is not commonly
used. It provides higher display quality. This type of monitor can hand
directly on a wall.
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59. Printer
• Printers are used to produce paper (commonly known as hardcopy)
output. When we talk about printers we refer to two basic qualities
associated with printers resolution and speed. Print resolution is
measured in terms of number of dots per inch (dpi). Print speed is
measured in terms of number of characters printed in a unit of time
and is represented as characters-per-second (cps), lines-per- minute
(lpm), or pages-per-minute (ppm).
• Based on the technology used, they can be classified as Impact or
Non-impact printers.
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60. • Impact printers
Impact printers use the typewriting printing mechanism wherein a
hammer strikes the paper through a ribbon in order to produce output.
Dot-matrix and Character printers fall under this category.
• Non-impact printers
Non-impact printers do not touch the paper while printing. They use
chemical, heat or electrical signals to etch the symbols on paper.
Inkjet, Deskjet, Laser, Thermal printers fall under this category of
printers.
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61. Plotter
• Plotters are used to print graphical output on paper. It interprets
computer commands and makes line drawings on paper using
multicolored automated pens. It is capable of producing graphs,
drawings, charts, maps etc. Computer Aided Engineering (CAE)
applications like CAD (Computer Aided Design) and CAM (Computer
Aided Manufacturing) are typical usage areas for plotters.
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