Input and Output Devices
Session - 4
As we discussed earlier computer system works on data and instructions, we give it to computer,
computer works on it and gives us processed output.
This means we give various types of data as input and take out as output, for this we need various
types of input and output devices.
An input device can send data to another device, but it cannot receive data from another device.
Examples of an input device include a computer keyboard and mouse, which can send data (input)
to the computer, but they cannot receive or reproduce information (output) from the computer.
An output device can receive data from another device, but it cannot send data to another device.
Examples of an output device include a computer monitor, projector and speakers, which can
receive data (output) from the computer, but they cannot send information (input) to the
computer.
An input/output device can send data to another device and also receive data from another
device. Examples of an input/output include a computer CD-RW drive and USB flash drive, which
can send data (input) to a computer and also receive data (output) from a computer.
Some device send data to another device as well receive data from another device these devices
are called as multifunction devices.
In short we say Input devices are hardware used to translate words, sounds, images, and actions
that people understand into a form that the system unit can process. For example, when using a
word processor, you typically use a keyboard to enter text and a mouse to issue commands. In
addition to keyboard and mice, there are a wide variety of other input devices. These include
pointing, scanning, image capturing, and audio-input devices.
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Different input devices :
One of the most common ways to input data is by keyboard. As mentioned in chapter 6,
keyboards convert numbers, letters, and special characters that people understand into electrical
signals. These signals. These signals are sent to and processed by, the system unit. Most keyboard
use an arrangement of keys given the name QWERTY. This name reflects the keyboard layout by
taking the letters of the first six alphabetic characters found on the top row of keys displaying
letters.
KEYBOARDS
One of the most common ways to input data is by keyboard. As mentioned earlier in session 3.
Keyboards convert numbers, letters, and special characters that people understand into electrical
signals. These signals. These signals are sent to and processed by, the system unit. The key
arrangement of all keyboards throughout the word is same….
There are a wide variety of different keyboard designs the most common types are
 Traditional keyboards-full boards-full-sized. Rigid, rectangular keyboards that include
function, navigational, and numeric keys.
 Flexible keyboards-fold or roll up for easy packing or storage. They are designed to provide
mobile users with a full-sized keyboard with minimal storage requirements.
 Ergonomic keyboards-similar to traditional keyboards. The keyboard arrangement,
however, is not rectangular and a palm rest is provided. They are designed specifically to
alleviate wrist strain associated with the repetitive movements of typing.
 Wireless keyboards- transmit input to the system unit through the air. By eliminating
connecting wires to the system unit, these keyboards provide greater flexibility and
convenience.
 PDA Keyboards-miniature keyboards for PDAs and smart phones to send e-mail, create
documents, and more.
FEATURES
A computer keyboard combines a typewriter keyboard with a numeric keypad, used to enter
numbers and arithmetic symbols. It also has many special-purpose keys. Some keys, such as the
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CAPS LOCK key, are toggle keys. These keys turn a feature on or off. Others, such as the ctrl key,
are combination keys, which perform an action when held down in combination with another
key. To learn more about keyboard features.
POINTING DEVICES
Pointing of course, is one of the most natural of all human gestures. Pointing devices provide a
comfortable interface with the system unit by accepting pointing gestures and converting them
into machine-readable input. There are a wide variety of different pointing devices, including the
mouse, joystick, touch screen, light pen, and stylus.
Mouse
A mouse controls a pointer that is displayed on the monitor. The mouse pointer usually appears
in the shape of an arrow. If frequently changes shape, however, depending on the application. A
mouse can have one, two, or more buttons which are used to select command options and to
control the mouse pointer on the monitor. Some mice have a wheel button that can be rotated
to scroll through information that is displayed on the monitor. Although there are several
different mouse types, there are three basic designs.
 Optical mouse has no moving parts and is currently the most widely used. It emits and
senses light to detect mouse movement. An optical mouse can be used on almost any
surface with high precision.
 Mechanical mouse has a ball on the bottom and is attached with a cord to the system unit.
As you move the pointer on the screen.
 Cordless or wireless mouse is a battery –powered device that typically uses radio waves
or infrared light waves to communicate with the system unit. These devices eliminate the
mouse cord and free up desk space.
Three devices similar to a mouse are trackballs, touch pads, and pointing sticks. You can use the
trackball, also known as the roller ball, to control the pointer by rotating a ball with your thumb
.You can use touch pads, to control the pointer by moving and tapping your finger on the surface
of a pad. You can use a pointing stick, located in the middle of the keyboard, to control the pointer
by directing the stick with one finger.
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TOUCH SCREENS
A touch screen is a particulars kind of monitor with a clear plastic outer layer. Behind this layer
are Crisscrossed invisible beams of infrared light. This arrangement enables someone to select
actions or commands by torching the screen with a finger. Touch screens are easy to use,
especially when people need information quickly. They are commonly used at restaurants,
automated teller machines (ATMs), and information centers.
Mobile and ATM machine screen are the examples of touch screen, now a days touch screen
monitors are also available.
JOYSTICKS
The joystick is a popular input device for computer games..
LIGHT PENS
A light pen is a light-sensitive pen like device. The light pen is placed against the monitor. This
closes a photoelectric circuit and identifies the spot for entering or modifying data. For example,
light pens are used to edit digital images and drawings.
STYLUS
A stylus is a pen like device commonly used with tablet PCs and PDAs. A stylus used pressure to
draw images on a screen. Often, a stylus interacts with the computer through Handwriting
recognition software. Handwriting recognition software translates handwritten notes into a form
that the system unit can process.
SCANNING DEVICES
Scanners move across text and images. Scanning devices convert scanned text and images into a
form that the system unit can process .There are four types of scanning devices: optical scanners,
card readers, bar code readers, and character and mark recognition devices.
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OPTICAL SCANNERS
An optical scanner, also known simply as a scanner, accepts documents consisting of text and /or
images and converts them to machine-readable form. These devices do not recognize individual
letters or images. There are two basic types of optical scanners: flatbed and portable.
Flatbed scanner is much like a copy machine. The image to be scanned is placed on a glass
surface and the scanner records the image from below.
Portable scanner is typically a handheld device that slides across the image, making direct
contact.
Optical scanners are powerful tools for a wide variety of end users, including graphics and
advertising professionals who scan images and combine them with text.
CARD READERS
A lot of people use a credit card, debit card, access (parking or building) card, and/or some type
of identification card. These cards typically have the user’s name, some type of identification
number, and signature embossed on the card. Additionally encoded information is often stored
on the card as well. Card readers interpret this encoded information. There are two basic types:
 By far the most common is the magnetic card reader. The encoded information is stored
on a thin magnetic strip located on the back of the card. When the card is swiped through
the magnetic card reader, the information is read.
 Radio frequency card readers are not as common but more convenient because they do
not require the card to actually make contact with the reader. The card has a small RFID
(radio frequency identification) microchip that contains the user’s encoded information
whenever the card is passed within a few inches of the card reader, the user’s information
is read.
BAR CODE READERS
You are probably familiar with bar code readers or scanners from grocery stores. These devices
are either handheld wand readers or platform scanners. They contain photoelectric cells than
scan or read bar codes, or the vertical zebra-striped marks printed on product containers.
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Almost all supermarkets use electronic cash registers and a bar code system called the Universal
Product Code (UPC). At the checkout counter, electronic cash registers use a bar code reader to
scan each product’s UPC code. The codes are sent to the supermarket’s computer, which has a
description, the latest price, and on inventory level for each product .The computer processes
this input to update the inventory level and to provide the electronic cash register with the
description and price for each product. These devices are so easy to use that many supermarkets
are offering customers self-checkout.
CHARACTER AND RECOGNITION DEVICES
Character and mark recognition devices are scanners that are able to recognize special characters
and mark. They are specially devices that are essential tools for certain applications. Three types
are
 Magnetic character recognition (MICR)—used by banks to automatically read those
unusual numbers on the bottom of checks and deposit slips. A special –purpose machine
known as a reader/sorter reads these numbers and provides input that allows banks to
efficiently maintain customer account balances.
 Optical-character recognition (OCR)-uses special preprinted characters that can be read
by a light source and changed into machine readable code. A common OCR device is the
handled wand reader. These are used in department stores to read retail price tags by
reflecting light on the printed characters.
 Optical-mark recognition (OMR)-senses the presence or absence of a mark. Such as a
pencil mark. OMR is often used to score standardized multiple-choice tests.
IMAGE CAPTURING DEVICES
Optical scanners, like traditional copy machines, can make a copy from on original. For example,
an optical scanner can make a digital copy of a photo-graph. Image capturing devices, on the
other hand, create or capture original images. These devices include digital cameras and digital
video cameras.
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DIGITAL CAMERAS
Digital cameras are similar to traditional cameras except that images are recorded digitally on a
disk or in the camera’s memory rather than on film and then downloaded, or transferred, to
your computer. You can take a picture, view it immediately. And even place it on your own
Webpage. Within minutes.
Digital photographs can be shared easily with others over the Internet.
DIGITAL VIDEO CAMERAS
Unlike traditional video cameras, digital video cameras record motion digitally on a disk or in the
camera’s memory. Most have the capability to take still images as well. Web-Cams are specialized
digital video cameras that capture images and send them to a computer for broadcast over the
Internet. Some Web-Cams are built-in while others are designed to be attached to the computer
monitor. Web camera mostly used for video conferencing.
AUDIO-INPUT DEVICES
Audio-input devices convert sounds into a form that can be processed by the system unit. By far
the most widely used audio-input device is the microphone. Audio input can take many forms,
including the human voice and music.
VOICE RECOGNITION SYSTEMS
Voice recognition systems use a microphone, a sound card, and special software. These system
allow users to operate computers and to create documents using voice commands. Portable voice
recognition systems are widely used by doctors, lawyers, and others to record dictation. These
devices are able to record for several hours before connecting to a computer system to edit,
store, and print the dictated information. Some systems are even able to translate dictation from
one language to another, such as from English to Japanese.
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OUTPUT
Output is processed data or information. Output typically takes the form of text, graphics, photos,
audio, and/or video.
Output devices are any hardware used to provide or to create output they translate information
that has been processed by the system unit into a form that humans can understand. There are
a wide range of output devices.
MONITORS
The most frequently used output device is the monitor. Also known as display screens, monitors
present visual images of text and graphics. The output is often referred to as soft copy. Monitors
vary in size, shape, and cost. Almost all, however, have some basic distinguishing features.
FEATURES
The most important characteristic of a monitor is its clarity. Clarity refers to the quality and
sharpness of the displayed images. It is a function of several monitor features, including
resolution, dot pitch, refresh rate, size, and aspect radio.
 Resolution is one of the most important features. Images are formed on a monitor by a
series of dots or pixels (picture elements).Resolution is expressed as a matrix of these
dots or pixels. For example many m monitors today have a resolution of 1,600 pixel
columns by 1,200 pixel rows of a total of 1,920,200 pixels. The higher a monitor’s
resolution (the more pixels), the clearer the image produced.
 Dot (pixel) pitch is the distance between each pixel. Most newer monitors have a dot pitch
of 31 mm (31/100thof a millimeter) or less. The lower the dot pitch (the shorter the
distance between pixels), the clearer the images produced.
 Refresh rate .indicates how often a displayed images is update or refreshed. Most
monitors operate at a rate of 75hertz, which means that the monitor is refreshed 75 times
each second. Images displayed on monitors with refresh rates lower than 75 hertz appear
to flicker and can cause eye strain. The faster the refresh rate (the more frequently images
are redrawn), the better the quality of images displayed.
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Size or active display area, is measured by the diagonal length of a monitor’s viewing area.
Common sizes are 15, 17, 19, 21, and 24 inches.
 Aspect ratio is determined by the width of a monitor divided by its height. Common aspect
ratios of monitors are (standard, similar to traditional television pictures) and 16:10 (side
screen).
FLAT-PANNEL MONITORS
Flat –panel monitors are the most widely used type of monitor today. Compared to other types,
they are thinner, more portable, and require less power to operate.
Almost all of today’s flat-panel monitors are LCD (liquid crystal display). There are two basic
types: passive –matrix and active-matrix. Passive-matrix or dual-scan monitors create images by
scanning the entire screen this type requires very little power, but the clarity of the images is not
as sharp.
Active-matrix or thin film transistor (TFT) monitors do not scan down the screen: instead, each
pixels independently activated. They can display more colors with better clarity.
Active-matrix monitors are more expensive and require more power.
CATHODE-RAY TUBES
Unit recently. The most common type of monitor for the office and the home was the cathoderay tube (CRT).These monitors are typically placed directly on the system unit or on the desktop.
CRTs are similar in size and technology to televisions. Compared to other types of monitors. Their
primary advantages are low cost excellent resolution. Their primary disadvantages are that they
are bulky, are less energy efficient, and occupy a considerable amount of space on the desktop.
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PRINTERS
You probably use a printer with some frequency to print homework assignments.
Photographs. And Web pages. Printers translate information that has been processed by the
system unit and present the information on paper. Printer output is often called hard copy.
FEATURES
There are many different types of printers, Almost all, however, have some basic distinguishing
features, including resolution, color capability, speed, and memory.
 Resolution for a printer is similar to monitor resolution. It is a measure of the clarity of
images produced. Printer resolution, however, is measured, in dpi (dots per inch). Most
printers designed for personal use average 1,200 dpi the higher the dpi. The better the
quality of images produced.
 Code capability is provided by most printers today. Users typically have the option to print
either with just black link or with color. Because it is more expensive to print in color.
Most users select black ink for letters. Drafts, and homework .Color is used more
selectively for final reports containing graphics and for photographs.
 Speed is measured in the number of pages printed per minute. Typically, printers of
personal use average 15 to 19 pages per minute for single-color (black) output and 13 to
15 pages for per minute for color output.
 Memory within a printer is used to store printing I instructions and documents waiting to
be printed. The more memory in a printer. The faster it will be able to create large
documents.
INK-JET PRINTERS
Ink-jet printers spray ink at high speed onto the surface of paper. This process not only produces
a letter-equality image but also permits printing to be done in a variety of colors, making them
ideal for select special applications. Ink-jet printers are the most widely used printers. They are
reliable. Quiet, and relatively inexpensive. The most costly aspect of ink-jet printers is replacing
the ink cartridges. For this reason, most users specify black ink for the majority of print jobs and
use the more expensive color printing for select applications. Typical ink-jet printers produce 17
to 19 pages per minute of black-only output and 13 to 15 pages of color output.
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LASER PRINTERS
The laser printer uses a technology similar to that used in a photocopying machine. Laser printers
use a laser light became to produce images with excellent letter and graphics quality. More
expensive than ink-jet printers, laser printers are faster and are used in application requiring highquality output.
There are two categories of laser printers .Personal Laser printers typically do not support color,
are less expensive, and are used by many single users. They typically can print 15 to 17 pages a
minute. Shared laser printers typically support color, are more expensive, and are used (shared)
by a group of users. Shared laser printers typically print over 50 pages a minute.
THERMAL PRINTERS
A thermal printers uses heat elements to produces images on heat-sensitive paper. These printers
are widely used with ATMs and gasoline pumps to print receipts.
Color thermal printers, known as dye-sublimation printers. Use specially treated paper to
produce very high-quality artwork and text. Due to their high purchase cost and the cost of the
special paper, these printers are typically limited to specialized application. They are, however,
widely used in professional art and design work where very high-equally color is essential.
OTHER PINTERS
There are several other types of printers. These printers include dot-matrix printers, plotters,
photo printers, and portable printers
 Dot-matrix printers form characters and images using a series of small pins on a print head.
Once a printer, they are inexpensive and reliable but quite noisy. In general, they are used
of tasks here high-quality output is not required.
 Plotters are special-purpose printers of producing a wide range of specialize output, form
graphics tablets and other graphical input devices, plotters create maps. Images, and
architectural and engineering drawings .Plotters are typically used by graphic artists,
engineers, and architects to print out designs, sketches, and drawings.
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 Photo printers are special-purpose printers designed to print photo-quality images from
digital cameras. Most photo printers print 3 *5”or 4*6” images on glossy. Photo-quality
paper.
 Portable printers are usually small and lightweight printers designed to work with a
notebook computer. Portable printers may be ink-jet or laser printers. Print in black and
white or color, and connect with USB or parallel port connections.
 That the monitor is refreshed 75 times each second. Images displayed on monitors with
refresh rates lower than 75 hertz appear to flicker and can cause eye strain. The faster the
refresh rate (the more frequently images are redrawn), the better the quality of images
displayed.
 Size, or active display area, is measured by the diagonal length of a monitor’s.
 Viewing area. Common sizes are 15, 17, 19, 21, and 24 inches.
 Aspect ratio is determined by the width of a monitor divided by its height. Common aspect
ratios for monitors are 4:3 (standard, similar to traditional television pictures) and
16:10(wide screen).
AUDIO-OUTPUT DEVICES
Audio-output devices translate audio information from the commuter into sounds that people
can understand the most widely used audio-output devices are speakers and headphones.
Digital music players, also known as digitals media players, are specialized devices for storing,
transferring, and playing audio files. Older players are only able to play music saved in a special
compressed audio file format known as MP3 .Today most players are able to use a wide variety
of audio files. Many are Apple’s iPod, Creative Zen, Microsoft Zune, and I River.
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