لخّصلي

Why this chapter
What is the use of the computer for us?The device driver provides correct commands to the controller,
interprets the controller register, and transfers data to and from device controller registers
as required for the correct device operation.Input
Devices
Keyboard, Mouse, Digitizing Tablet, Track Ball, Joystick, TouchScreen, Light Pen,
Speech Recognition System, Digital camera, Scanner, Magnetic Ink Character
Recognition (MICR), Optical Character Recognition (OCR), Optical Mark
Recognition (OMR), Barcode Reader
Output
Devices
Monitor, Visual Display Terminal, Printer, Plotter, Computer Output on Microfi lm
(COM), Video Output System, Audio Response System
Input-
Output
Devices
Hard disk drive, Floppy disk drive, USB drive, CD drive, DVD drive
Table 4.1 I/O devices
4.3 INPUT DEVICES
Input devices allow users and other applications to input data into the computer, for processing.Source data entry devices
o Audio input--speech recognition
o Video input--digital camera
o Scanner--hand-held scanner, flat-bed scanner
o Optical Scanner--OCR, OMR, MICR, barcode reader
The input is provided to the computer using an input device, and must be translated to a form
that the computer can understand.Also in a portable computer, the
PC Card connects to the PC Card slot on it.
The I/O ports are the external interfaces that are used to connect input and output devices like
printer, modem and joystick to the computer.4.5.3.2 Optical Character Recognition (OCR)
OCR is a technique for the scanning of a printed page, translating it, and then using the OCR
software to recognize the image as ASCII text that is editable.Plotters are mainly used for drawings in AUTOCAD (computer assisted drafting),
Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) applications.In brief, the input unit accepts input data from the user via input device, transforms the input data
in computer acceptable form using input interface for the input device and provides the
transformed input data for processing.Touch screen are generally used in applications like Automated Teller Machine (ATM), public
information computers like hospitals, airline reservation, railway reservation, supermarkets, etc.Other common optical input devices are magnetic ink character reader used
for Magnetic Ink Character Recognition (MICR), optical mark reader used for Optical Mark
Recognition (OMR), optical character reader for Optical Character Recognition (OCR) and
Barcode Reader.The OMR reader scans the forms, detects the mark that
is positioned correctly on the paper and is darker than the surrounding paper, and passes this
information to the computer for processing by application software.4.6.1.2 Plotter
A plotter is used for vector graphics output to draw graphs, maps, blueprints of
ships, buildings, etc.In addition to the above ports, other ports also exist like Musical Instrument Digital Interface
(MIDI) port to connect musical instruments like synthesizers and drum machines, PC expansion
boards, and PC card and many more.In brief, the output unit accepts output data from computer via output device, transforms the
output information to human readable form using the output interface of output device and
provides the transformed output to user.In addition to the above devices, the input to a computer can also be provided from a storage
device on the computer, another computer, or another piece of equipment, such as a musical
instrument, thermometer or sensors
4.4 HUMAN DATA ENTRY DEVICES
Input devices that require data to be entered manually to the computer are identified as human
data entry devices.Digitizing tablet is
used for Computer Aided Design (CAD) for the design of buildings, automotive designs, and
designing of maps, etc.Working The tablet contains circuit that can detect the movement of pen on the tablet, convert
the movements into digital signals and send the digital signal to the computer.Scanners
come with utility software that allow the stored scanned documents to be edited, manipulated
and printed.The
processed data, presented to the user via the output devices could be text, graphics, audio or
video.In a drum plotter, pens mounted on the carriage are
stationary and move only horizontally; for vertical movement, the drum on which the paper is
fixed moves clockwise and anti-clockwise.The projector is mainly used to display
visual output to a large gathering of people required for the purposes of teaching, training,
meetings, conference presentations, etc.4.1 INTRODUCTION
A computer interacts with the external environment via the input-output (I/O) devices attached to
it. Input device is used for providing data and instructions to the computer.Moreover, it provides an easy way to select and
choose commands from menus, dialog boxes, icons, etc.Right Click involves pressing the right button on mouse and releasing it. Right click
displays a menu that contains options like cut, copy, paste, font, paragraph, etc.4.4.2.4 Digitizing Tablet
Features It is an input device used primarily to input drawings, sketches, etc.Open
source software like Audacity is used for recording and editing of audio files
4.5.2 Video Input Device
Video input is provided to the computer using video camera and digital.Soft Copy Devices
o Monitor
o Visual Display Terminal
o Video Output
o Audio Response
The output device receives information from computer in a machine readable
form.The speed of dot matrix
printer lies between 200 and 600 characters per second (cps) and their resolution ranges
from 72 to 360 dpi.Dot matrix printers are
commonly used for printing in applications like payroll and accounting.Plotters draw continuous and accurate lines, in contrast to printers where a line is drawn
as closely spaced dots.COM is suited for
storing large amounts of data for manuals and archive records for long periods of time that have
to be referenced occasionally.The number of colors displayed by a color monitor
varies with the kind of color adapter attached to it--CGA, EGA, VGA, XGA and SVGA.Monitors may be Cathode Ray Tube (CRT) monitors that look like a television or
Liquid Crystal Display (LCD) monitors that have a high resolution,
flat screen, flat panel display.Irrespective of the kind of input data provided to a computer, all input devices must
translate the input data into a form that is understandable by the computer, i.e., in
machine readable form.The output data is provided through output devices like display screen, printer, plotter
and speaker.Human data entry devices
o Keyboard
o Pointing devices--mouse, trackball, joystick, digitizing tablet
o Pick devices--light pen, touch screen
?A
sound card (Figure 4.9 (i)) translates analog audio signals from microphone into digital codes
that the computer can store and process.Some of the documents that are primarily
scanned using hand-held scanners are price tags, label and ISBN number on books.The OCR software translates the array of dots into text that the computer
can interpret as words and letters.To recognize the words and letters of text, the OCR software
compares the pattern on the scanned image with the patterns stored inside the computer.4.5.3.5 Barcode Reader
Barcodes are adjacent vertical lines of different width that are machine readable.Dot matrix printers can print alphanumeric characters, special
characters, charts and graphs.Microfilm can
be indexed to facilitate retrieving information from it. For reading images stored on microfilm, a
microfilm reader is used.4.6.2 Soft Copy Devices
The output obtained in an intangible form on a visual display, audio unit or video unit is called
soft copy output.In addition to recording and playing the sound, the software allows editing of sound,
like cutting, copy, amplification and creation of vibrant sound effects.The I/O devices are connected to the computer via
the serial and parallel ports, Universal Serial Bus (USB) port, Firewire port, etc.Normally, two to four USB ports are provided on a PC. USB allows different
devices to be connected to the computer without requiring re-boot of the computer.After processing the
input data, computer provides output to the user via the output device.The input data is provided through input devices, such as--keyboard, mouse, trackball
and joystick.Input data can also be provided by scanning images, voice recording, video
recording, etc.The keyboard controller stores the code of pressed key in keyboard buffer and informs
the computer software that an action has happened on the keyboard.Due to a time gap between pressing of a key on keyboard and reading by the system
software, keyboard buffer is designed to store many keystrokes together.Optical Mouse uses a Light Emitting Diode (LED) and a sensor to detect the movement of
mouse.Joystick is mainly used to control the speed of the cursor and is thus popular in games involving
speed like racing and flying games.It can be used for making telephone calls, for audio
and video conferencing over Internet, to record voice, to create audio files and embed these files
to be sent over e-mail, or, to translate spoken words into text, etc.Audio input can be recorded on an mp3 recorder and provided as an input to computer.Scanner accepts the source paper document, scans the document and translates
it into a bitmap image to be stored on the computer.The optical character reader stores the scanned image as bitmap image which is a
grid of dots.The text
files generated via OCR can be stored in different formats.Hand-held barcode readers are generally used in
departmental stores to read the labels, and in libraries to read labels on books.4.6 OUTPUT DEVICES
Output devices provide output to the user, which is generated after processing the input data.Hard Copy Devices
o Printer
o Plotter
o Computer Output on Microfilm (microfiche)
?Impact printers use the typewriter approach of physically striking a typeface against the paper
and inked ribbon.Dot matrix printers, daisy wheel printers and drum
printers are examples of impact printers.Dot matrix printers normally come in two sizes--80 column printer
and 132 column printer.These printers are slow, can only print text (not graphics), and
are costly in comparison to dot matrix printers.The laser printer can print 5-24 pages of text per minute and their
resolution ranges from 400 to 1200 dpi.Laser printers are used in applications requiring high quality voluminous
printing.COM is used for storing output in banking and insurance
applications, medical X rays, etc.Visual output devices like computer
monitor, visual display terminal, video system and audio response system are common soft copy
output devices.The signals
are sent to the speakers via the sound card that translates the digital sound back into analog
signals.The audio response from the computer may be generated by synthesizing the input
human speech to give audio output, or may be a result of a set of rules that are used to create
artificial speech.Serial port is used to connect external modems, plotters, barcode reader , etc.The I/O hardware includes
ports, buses and device controllers for different devices, and I/O devices.The input unit gets the data and programs from various input devices and makes them
available for processing to other units of the computer.This
processed data is converted to human readable form by the output interface of output
device.Hard disk drive, floppy disk
drive, optical disk drives are examples of I/O devices.Cursor is a vertical line, an underscore, blinking line, etc.The
keyboard has five sections (1) Typing keys (1, 2, 3..., A, B, C...), (2) Numeric keypad (numeric
keys on right side), (3) Function keys (F1, F2....Working When a key is pressed, keyboard interacts with a keyboard controller and keyboard
buffer.The computer software
checks and reads the keyboard buffer and passes the code of pressed character to the system
software.Mouse,
trackball, joystick and digitizing tablet are some of the common pointing devices.Mouse is used extensively, while
working with graphics elements such as line, curve, shapes, etc.When the ball of mouse moves, the rollers sense the horizontal and vertical
movement and sensors sense the speed of movement.Left Click or Click means pressing the left button of mouse and releasing it. Clicking is
used to select a button, command or icon on the screen.Instead of moving the whole device to
move the cursor on computer screen, trackball requires the ball to be rotated manually with a
finger.Drawings can be made on the tablet using a pen, and is provided as input to computer, where, a
location on the tablet corresponds to a specific location on the screen.4.4.3.2 Touch Screen
Features It is an input device that accepts input when the user places a fingertip on the computer
screen.In addition to the glass panel with sensors, it has a device driver, and a
controller that translates the information captured by the glass panel sensors to a form that the
computer can understand.Source data entry devices do not require data to be typed-in, keyed-in or
pointed to a particular location.Sound card also translates back the digital sound into
analog signals that can be sent to the speakers.They are generally used by
people who have difficulty in typing, people with disabilities or by corporate world for dictation.The images are digitized and can be
compressed and stored in the computer disk.A video capture card allows the user to connect video devices like camcorders to the
computer.Computer vision has applications in areas like robotics and industrial
processing.It is an optical input device
and uses light as an input source to convert an image into an electronic form that can be stored
on the computer.To edit the scanned text, you
need OCR software.4.5.3.3 Magnetic Ink Character Recognition (MICR)
MICR is used in banks to process large volumes of cheques.It is used for
recognizing the magnetic encoding numbers printed at the bottom of a cheque.The numbers on
the cheque are human readable, and are printed using an ink which contains iron particles.The
optical mark reader detects the presence of mark by measuring the reflected light.The output could be on a paper or on a film in a tangible form, or, in an intangible form as
audio, video and electronic form.Printer, plotter and microfiche are common hard copy output devices.Printers are generally
used to print textual information, but nowadays printers also print graphical information.Drum
printers are generally used for voluminous print outputs.Laser Printers provide highest quality of text and graphics printing.The paper is stationary and the pens mounted on the carriage move horizontally and vertically to
draw lines.4.6.1.3 Computer Output on Microfilm
A microfilm is in a fiche or roll format, and is used to record computer output
directly from the computer tape or cartridge.The soft copy allows corrections to be made, can be stored, and, can be sent via
E- to other users.Dot Pitch--the diagonal distance between two colored pixels on a display screen, and
3.4.6.2.2 Visual Display Terminal
A monitor and keyboard together are known as Visual Display Terminal (VDT).4.6.2.4 Audio Response
A complete sound system consists of sound card, microphone, speaker and the appropriate
software.Audio output device like speakers,
headset or headphone is used for audio output sound from computer.Audio output is commonly used for customer service in airlines, banks, etc.Since data is
transmitted serially as single bits, serial ports provide slow speed data transmission.USB
also has the plug and play feature which allows devices ready to be run simply by
plugging them to the USB port.Firewire (IEEE 1394) It is used to connect audio and video multimedia devices like
video camera.Device Driver is software via which the operating system communicates with the device
controllers.The device drivers hide the differences among the different device
controller and present a uniform interface to the operating system.The aim of this chapter is to introduce the
different kinds of input and output devices.Different kinds
of input and output devices are used for different kinds of input and output requirements.The input unit is responsible for providing input to the computer and the output unit
is for receiving output from the computer.The transformation of the input data to machine readable form is
done by the input interface of input device.The output unit gets the processed data from the computer and sends it to output devices
to make them available to the user of computer.The data input to a computer can be in the form of text, audio, video, etc.The data is entered manually by the user or with minimal user
intervention.Input devices are classified as follows--
?The position of cursor indicates the location on monitor where the typed-in character
will be displayed.The modern keyboards
are QWERTY keyboard (Q, W, E, R, T, Y are the sequence of keys in top row of letters).on top side), (4) Control keys (cursor keys, ctrl,
alt....), and (5) Special-purpose keys (Enter, shift, spacebar...).Optical mouse requires an opaque flat surface underneath it. Optical mouse was
introduced by Microsoft in 1999.Optical mouse is better than physical mouse as there is no
moving part that can cause wear and tear, and dirt cannot get inside it.
Working In a physical mouse, rollers and sensors are used to sense the direction and rate of
movement of mouse.When an optical mouse is moved, a beam of light is reflected from its
underside.4.4.2.2 TrackBall
Features Trackball is a device that is a variant of the mouse but has the functionality of mouse.The plastic cover contains the circuit that detects the movement of stick and sends the
information to computer.Description Digitizing tablet consists of two parts--electronic tablet and pen.4.4.3.1 Light Pen
Features It is a light sensitive pen-like input device and is used to select objects directly on the
computer screen.Working Touch screens have an infrared beam that criss-cross the surface of screen.Some touch
screens have ultrasonic acoustic waves that cross the surface of screen.4.5 SOURCE DATA ENTRY DEVICES
Source data entry devices are used for audio input, video input and to enter the source document
directly to the computer.Audio input devices like a microphone is used to input a person's voice into the computer.The audio input along with the software for voice
recognition forms the speech recognition system or voice recognition system.The user can dictate the commands to the
computer, instead of typing them.The digital camera digitizes
images, compresses them and stores them on a memory card like flash memory.Scanner is used to input data
directly into the computer from the source document without copying and typing the data.The scanned documents are converted and stored as an
image in the computer memory.The document to be scanned is placed on the glass top, which activates the light
beam beneath the glass top and starts the scan from left to right.OCR uses optical character reader
for recognition.Thus, you cannot edit the text that has been scanned.MICR uses magnetic ink character reader for character recognition.When a cheque is passed through Magnetic Ink Character Reader, the magnetic field causes the
read head to recognize the characters or numbers of cheque.4.5.3.4 Optical Mark Recognition (OMR)
OMR is used to detect marks on a paper.For this, it uses a beam of
light that is reflected on the paper with marks, to capture presence and absence of marks.OMR is widely used to read answers of objective type tests, where the student marks an answer
by darkening a particular circle using a pencil.Barcodes are read using reflective
light by barcode readers.This information is input to the computer which interprets the code
using the spacing and thickness of bars.They enable faster service to the
customer and are also used to determine the items being sold, number of each item sold or to
retrieve the price of item.Output devices are classified as follows--
?4.6.1 Hard Copy Devices
The output obtained in a tangible form on a paper or any surface is called hard copy output.The
print quality (sharpness and clarity of print) of the printer is determined by the resolution of the
printer.Resolution is measured in dots per inch (dpi).Printers with a high resolution (more dpi)
provide better quality output.Printers are classified into two categories--impact printer and non-impact printer.They produce letter
quality document which is better than a document printed by a dot matrix printer.Daisy wheel printers are used where high
quality printing is needed and no graphics is needed.They use electro-static chemicals and
ink-jet technologies.They
produce high quality output and can be used for printing text and graphics both in black and
white, and color.Ink-jet
printers are commonly found in homes and offices.Plotters use pens of different colors (cyan, magenta, yellow and black) for
drawing.Plotters are of two
kinds--drum plotter and flatbed plotter.Monitors are
available in various sizes like 14, 15, 17, 19 and 21 inches.Resolution of Screen--the number of pixels in horizontal and vertical direction.Nowadays, LCD monitors are generally used.A keyboard is
used to input data and monitor is used to display the output from the computer.The dumb terminals do not have processing and programming capabilities.Smart
terminals have built-in processing capability but do not have its own storage capacity.Printers and
scanners are connected to ports on the backside of the computer.Application programs use an I/O device by issuing commands and exchanging data with
the device driver.Operating system ------ Device Drivers -------- Device Controllers -------- DevicesBut to do any of these things, we
should be able to provide the data to the computer and also get the output from it. The input
devices and output devices are used this purpose.The I/O devices that are
attached, externally, to the computer machine are also called peripheral devices.In this
chapter, we shall discuss different kinds of input devices and output devices.4.2 INPUT-OUTPUT UNIT
An I/O unit is a component of computer.The I/O unit is composed of two parts--input unit and
output unit.The processed data sent to the output device is in a machine understandable form.In addition to input devices and output devices, some devices function as both input and output
devices.The I/O devices provide the input to computer as well as get output from computer.The
I/O devices are used by both the input unit and the output unit.The translation is done by the input interface of the input
device.4.4.1 Keyboard
Features Keyboard is a common input device.For inputting the data, the user types the data
using the keyboard.When the data is being typed, the display monitor displays the typed data.Standard keyboard contains 101 keys which are arranged in the same order as a typewriter.4.4.2 Pointing Devices
Pointing devices are used for providing the input to computer by moving the device to point to a
location on computer monitor.Operations like move, click and drag can be performed using the pointing devices.The mouse may also be used to position the cursor on
screen, move an object by dragging, or select an object by clicking.It
requires a smooth, dust free surface, such as a mouse pad, on which it is rolled.These pulses of light determine the direction and rate of movement.Double Click means pressing the left button of mouse twice successively, without
moving the mouse, and then releasing the mouse.Drag and drop is used for moving folders, files and icons to new
locations on the screen.Trackball is generally built in laptops since
there is no space for the mouse to move on the lap.Trackballs come in various sizes--small and
big.4.4.2.3 Joystick
Features Joystick is a device which is commonly used for playing video games.The direction of push of the stick and the amount of
deflection determines the change in position and the change in speed, respectively.4.4.3 Pick Devices
Pick devices are used for providing input to the computer by pointing to a location on the
computer monitor.Description and Working The pen contains a photocell in a small tube.When a
fingertip is touched on the screen, the beam is broken, and the location is recorded.When a fingertip is
touched on the screen, the wave is interrupted, and the location is recorded.The recorded
location is sent to the computer via the controller of touch screen, in a form that the computer
can understand.4.5.1 Audio Input Device
Audio input can be provided to the computer using human voice or speech.Audio input to the
computer can be used for different purposes.Translating spoken words into text is also known
as speech recognition or voice recognition.The computer has to be trained to recognize the voice of user
using the speech patterns and pronunciation of words.The system thus adapts to the voice of
user.Speech recognition systems are costly and difficult to develop.It is
placed on the computer above the screen to capture the images of the user who is working on the
computer.Digital camera works like video camera but can capture still images.The video files can be
edited using software like VLC media player.4.5.3 Optical Input Devices
Optical input devices allow computers to use light as a source of input.Scanner is an example of
optical input device.4.5.3.1 Scanner
Scanner is an input device that accepts paper document as an input.The
input data to be scanned can be a picture, a text or a mark on a paper.The denser the bitmap, the higher is the
resolution of the image.The quality of scan increases with the increase in resolution.Hand-held Scanners are portable and are placed over the document to be scanned.They
consist of light emitting diodes.Hand-held scanners have to be moved at a constant
speed over the document to be scanned, to get good quality scans.They are preferably
used for low volume of documents, small pictures or photos.It is a box shaped machine
similar to a photocopy machine and has a glass top and a lid that covers the glass.They are largely used to
scan full page documents.The readers are generally used in
banks to process the cheques.OMR uses
an optical mark reader to read the marks.OMR is also used to read forms, questionnaires,
order forms, etc.Barcode readers are fast and accurate.The received output is translated to a human understandable form.The translation is done
using the output interface of output device.The
hard copy can be stored permanently and is portable.The devices that generate hard copy output are called hard copy devices.Impact printers
are low-cost printers useful for bulk printing.Dot Matrix Printers (Figure 4.17) print one i character at a time.Some dot matrix
printers can print in both directions - left to right and right to left.The
speed of daisy wheel printers is about 100 cps.The print head of the printer is like a daisy
flower, hence the name.Laser printers process and store the entire page before printing and are also known as
page printers.The copy of the image on microfilm retains its original clarity.A screen is used for viewing the enlarged images.The devices that
generate soft copy output are called soft copy devices.The monitor is provided along with the computer, to view
the displayed output.A monochrome display monitor uses only one color to display text and color display
monitor can display 256 colors at one time.The
CGA monitor supports four colors and SVGA supports around 16,000,000 colors.An image on the monitor is created by a configuration of dots, also known as pixels.Refresh Rate--the number of times per second the pixels are recharged so that their glow
remains bright.Intelligent
terminals have both built-in processing and storage capacity.4.6.2.3 Video Output
Screen image projector or data projector is an output device that displays
information from the computer onto a large white screen.Audio response provides audio output from the computer.It is also used in
video conferences, surveys, etc.Audio response is used by visually impaired to read information
from the screen.For speech impaired people, audio response helps them to communicate with
other people.Devices such as network
adapters and sound cards are connected to expansion slots inside the computer.Parallel Port A parallel port is an interface for connecting eight or more data wires.The
data flows through the eight wires simultaneously.USB Port Nowadays, USB is a common and popular external port available with
computers.Hard
disk drive and new DVD drives connect through firewire.4.8 WORKING OF I/O SYSTEM
The working of I/O system combines I/O hardware and I/O software.The I/O software is the
device driver software that may be embedded with operating system or comes with each device.I/O Devices are attached to computer via the ports of computer.It controls the signals on the
wires of port or bus.The controllers have one or more registers for data and control
signals.Table 4.1 lists the different I/O devices.The data may be entered by typing or keying in, or by pointing a device to a
particular location.Cursor moves with each typed
character.Description The design of a keyboard is similar to a standard typewriter.Some keyboards have 110 keys,
where the extra keys are designed to work with the Windows operating system.The input data is not typed; instead, the data is entered by moving
the pointing device.4.4.2.1 Mouse
Features It is the most common pointing input device.So, the cursor can be positioned at any location
on the screen by simply moving the mouse.The wheel of the mouse is used for the up and down movement, for example, scrolling a
long document.A mouse is classified as physical mouse or optical mouse.This information is passed to computer via
the mouse chord.This information
is sent to computer via the mouse chord.Drag means pointing
mouse to an object on screen, pressing the left button of mouse, keeping it pressed and
moving the mouse to point to a new location.The trackball device remains stationary.Description It is a stick with its base attached to a flexible rubber sheath inside a plastic cover.The position of the stick movement is given by the x and y coordinates
of the stick.The electronic
tablet is a flat bed tablet.Each position on the tablet corresponds to a fixed position on the screen.The input data is not typed; the data is entered by pointing the pick device
directly on the computer screen.Description Touch screen consists of a clear glass panel that is placed over the view area of
computer screen.The computer can be operated using voice commands.Video camera can capture full motion video images.The information
from the digital camera can be brought into the computer and stored.Hand-held scanner and flat-bed scanner are the two common types of scanners.Flat-bed Scanners provide high quality scan in a single pass.The reading speed of MICR is faster than OCR.The pattern of
marks is interpreted and stored in the computer.Goods available
at supermarkets, books, etc.use barcode for identification.4.6.1.1 Printer
A printer prints the output information from the computer onto a paper.Different kinds of printers are available for different types of
applications.Daisy Wheel Printers (Figure 4.18) print one character at a time.Drum Printers are line printers.They are expensive and faster than character printers
but produce a low quality output.Non-Impact Printers do not hit or impact a ribbon to print.Non-impact printers are faster and quieter than impact printers.Ink-jet printers and laser printers are non-impact printers.Ink-jet Printers spray ink drops directly on the paper like a jet .Their
resolution is more than 500 dpi.They produce high quality graphics and text.Plotter is a slow output device and is expensive.In a flatbed plotter, the paper is fixed on a flat bed.Computer Output on Microfilm (COM) is a high
speed and low cost process.It can produce data in microfilm form at a much faster speed from
that of a paper printer.The soft copy output requires a computer to be read or used.A monitor is of two kinds - monochrome display monitor and color display
monitor.The clarity
of image on the computer screen depends on three factors--
1.More
the number of pixels, the sharper is the image.Terminals are categorized as dumb, smart and intelligent
terminals.4.7 I/O PORT
The peripheral devices can be connected to computer in several ways.They can transmit eight bits of data in
parallel.As a result, parallel ports provide high speed data transmission.A single USB port can support connection of up to 127
devices.The working of I/O system is described as follows--
?There are many standard
ports available on the backside of the computer case like serial port and parallel port.If
one or more devices use a common set of wires, it is called a bus.For example, PCI bus,
PCI Express bus, etc.Device Controller operates on a bus, a port or a device.Controller may be simple like a serial port controller for a serial port, or, complex
like a SCSI controller.Some devices have their own built-in controllers.We may want to process data, write project reports, listen
to sound recordings, watch a movie and do many more things.4.2.1 Input Unit
?4.2.2 Output Unit
?Figure 4.1 shows some
users working in an office.It is provided along with the computer, and is
easy to use.It is used for entering the text data.The cursor on the computer monitor moves with the moving pointing device.The key benefit of using a
mouse is that the cursor moves with the mouse.Physical Mouse has a rubber ball on the bottom side that protrudes when the mouse is moved.Using the mouse The mouse can be used in five different ways, as follows--
?Moving the mouse by
hand moves the cursor on computer screen.The cursor moves in the direction in which
the mouse moves.It is used to start a program or open a
folder.Drag and Drop drags an object and drops it at another location.Description Trackball looks like an upside-down mouse.The cursor on the computer screen moves in the
direction in which the ball is moved.The buttons on trackball are used in the same way as mouse
buttons.Working Trackball works in the same way as a physical mouse.The pen looks like a ball pen but has an electronic head.The pen in
moved on the tablet.Light pen and touch screen are some common pick devices.It is used for making drawing, graphics and for menu selection.Figures and
drawings can be made by moving the pen on computer screen.When the pen is moved
on the screen, light from the screen at the location of pen causes the photocell to respond.The
electric response is transmitted to the computer that can identify the position on screen at which
the light pen is pointing.The computer selects the option from the menu of screen to which the finger points.Webcam is a common video camera device.Computer vision is an area of computer science
that deals with images.They are difficult to use if
there is a need to scan a full page document.These
numbers are magnetized.The numbers in the bottom of the cheque include the bank number,
branch number and cheque number.The hard copy output can be read or used
without a computer.Impact printers can print a character or an entire line at a time.They are faster and expensive than impact
printers.4.6.2.1 Monitor
Monitor is a common output device.The common resolution of computer
screen is 800x600 and 1024x768,
2.Parallel port is
used to connect printer to the computer.Serial Port A serial port transmits one bit of data through a single wire.It is an expensive technology and is used for large data movement.It has data transfer rate of up to
400 MB/sec.Each device has its own device driver, and a device controller which is
specific to the device.????The data is entered by pointing the mouse
to a location on the computer screen.Description Mouse is a small hand-held device having two or three buttons on its upper side.In
addition to the buttons, mouse also has a small wheel between the buttons.Pointing points to a location or object on the computer screen.??for the
item on which the mouse is pointing.??The object gets dragged to the new location
along with the mouse.When the left button of mouse is released, the object gets dropped
at the new location.It is easy to use and takes less space than a mouse.??The marks are recognized by their darkness.?They can print only in black and white.??They can print 200-2500 lines per minute.??The standard roll film is 16 mm wide with a film image that is 1/24 of the
original document.The monitor is
connected to the computer by a cable.???????