Input and Output Devices: Computer Awareness Notes
INPUT DEVICES:
We interact with computers in several ways. e.g., we type in
a keyboard, swipe a screen, use the mouse to click and browse. A computer receives
information from all these devices we use. Such devices are called input
devices.
Input device is a
peripheral (piece of computer hardware equipment) used to provide data and
control signals to a computer. Examples
of input devices include Keyboard, Mouse, Scanners, Trackpad and Joystick.
A) Keyboard
A computer keyboard is a
typewriter-style device which uses an arrangement of buttons or keys to act as
mechanical levers or electronic switches.
The most popular type is
the QWERTY design, which is based on typewriter keyboards.
i) Alphabet Keys: The
alphabet keys are lined in QWERTY type Aa-Zz
ii) Function Keys: The
function keys are lined along the top of the keyboard and labeled F1 through
F12.
iii) Control Keys: A Control
key is a modifier key which, when pressed in conjunction with another key,
performs a special operation (for example, Ctrl+C); similar to the Shift key,
the Control key rarely performs any function when pressed by itself.
B) Mouse
Used to move or position
a cursor on a computer screen. It is a pointing device that detects
two-dimensional motion relative to a surface. This motion is typically
translated into the motion of a pointer on a display, which allows for fine
control of a graphical user interface.
Physically, a mouse
consists of an object held in one’s hand, with one or more buttons. Mice often
also feature other elements, such as touch surfaces and “wheels”, which enable
additional control and dimensional input.
i) Typical Mouse Buttons: Three-button
scroll mouse has become the de facto standard. Users most commonly employ the
second button to invoke a contextual menu in the computer’s software user
interface, which contains options specifically tailored to the interface
element over which the mouse cursor currently sits.
By default, the primary
mouse button (used for clicking the pointed/selected object) sits located on
the left-hand side of the mouse
ii) Mechanical Mouse: The ball
mouse has two freely rotating rollers. They are located 90 degrees apart. One
roller detects the forward-backward motion of the mouse and other the
left-right motion.
iii) Optical Mouse: Optical
mice rely entirely on one or more light-emitting diodes (LEDs) and an imaging
array of photodiodes to detect movement relative to the underlying surface
iv) Mouse with Scroll Wheel: A scroll
wheel is a hard plastic or rubbery wheel on a mouse that is perpendicular to
the mouse surface. It is normally located between the left and right mouse
buttons. It is used, as the name suggests, for scrolling.
C) Trackpad
A touchpad or trackpad is
a pointing device featuring a tactile sensor, a specialized surface that can
translate the motion and position of a user’s fingers to a relative position on
the operating system that is outputted to the screen. Touchpads are a common
feature of laptop computers. They are available in the following types:
i) Resistive: A
resistive touchpad allows the users to use equipment to touch the screen or
application. Resistive touchpads, however, don’t allow the user to use his
fingers to activate the touchpad capability.
ii) Electromagnetic: The
electromagnetic touchpad works much like the resistive touchpad. This touchpad
is also operated by an instrument. The instrument is different than a stylist
used in resistive touchpads because the electromagnetic touchpad is operated by
a light pen.
iii) Capacitive: The
capacitive touch pad is highly preferred over resistive and electromagnetic
touchpads. Capacitive touchpads may be used for public access to Internet,
guiding systems or cell phones.
D) Joystick
A joystick is an input
device consisting of a stick that pivots on a base and reports its angle or
direction to the device it is controlling. Joysticks are often used to control
video games, and usually have one or more push-buttons whose state can also be
read by the computer.
E) Scanner
A scanner is a device
that captures images from photographic prints, posters, magazine pages, and
similar sources for computer editing and display. Scanners come in hand-held,
feed-in, and flatbed types and for scanning black-and-white only, or colour.
OUTPUT DEVICES:
After a computer performs
its function, it interacts with us through several ways. e.g., it displays
information in a monitor or prints a page in the printer.
An output device is any
piece of computer hardware equipment used to communicate the results of data
processing carried out by a computer to a human (in most cases). Output devices
convert the electronically generated information into human-readable form.
Examples of output
devices are Display/Monitor, Speaker, Printer and Projectors.
A)
Display/Monitor
A display device is an
output device for presentation of information in visual or tactile form.
i) CRT (Cathode Ray TubE): A cathode
ray tube (CRT) is a specialized vacuum tube in which images are produced when
an electron beam strikes a phosphorescent surface. Most desktop computer
displays make use of CRTs.
ii) LED (Light-Emitting
DiodE): Light-emitting diode (LED) computer
monitors do not use cold-cathode technology and fluorescent technology.
Instead, light diodes illuminate the screen in one of two different ways, or a
combination of both.
iii) LCD (Liquid-Crystal
Display): A liquid-crystal display better known
as (LCD) is a flat panel display, electronic visual display, or video display
that uses the light modulating properties of liquid crystals. Liquid crystals
do not emit light directly.
iv) Tactic Display: A tactile
electronic display is a kind of display device that presents information in
tactile form. The two most popular kinds of tactile electronic displays.
B) Speaker
The computer speakers are
one of the most common output devices used with computer systems. They receive
audio input from the computer’s sound card and produce audio output in the form
of sound waves. The computer speakers have an internal amplifier which allows
you to increase the volume or amplitude of the sound.
C) Printer
A printer is a device
that accepts text and graphic output from a computer and transfers the
information to paper, usually to standard size sheets of paper. Printer types
are given below:
i) Dot Matrix: Dot matrix
printing is a type of computer printing which uses a print head that moves
back-and-forth, or in an up-and-down motion, on the page and prints by impact,
striking an ink-soaked cloth ribbon against the paper, much like the print
mechanism on a typewriter.
ii) Inkjet: Inkjet
printing is a type of computer printing that recreates a digital image by
propelling droplets of ink onto paper, plastic, or other substrates. Inkjet
printers are the most commonly used type of printer, and range from small inexpensive
consumer models to expensive professional machines
iii) Bubble Jet: Bubble-jet
printers use special heating elements to prepare the ink. Bubble-jet printers
use serial printing process.
iv) Laser: A laser
printer is a printer for computers. It uses LED-technology to get small
particles of toner from a cartridge onto paper.
v) Plotters: The
plotter is a computer printer for printing vector graphics. In the past,
plotters were used in applications such as computer-aided design, though they
have generally been replaced with wide-format conventional printers. A plotter
gives a hard copy of the output. It draws pictures on a paper using a pen.
D)
Projector
The projector is a device
that projects computer output onto a white or plane screen that is wall, ceiling
or tripod mounted. It is widely used in auditoriums and classrooms for
instruction and slide presentations.
Screen Capture/Display
Resolution Measurement
DPI: Dots Per Inch
PPI: Pixels Per Inch
PPCM: Pixels Per Centimeter
Display
Devices/Technologies
CRT: Cathode Ray Tube
HDTV: High Definition Television
LCD: Liquid Crystal Display
LED: Light Emitting Diode
OLED: Organic Light-Emitting Diode
Ports and
Other Concepts
A port serves as an
interface between the computer and other computers or peripheral devices. Ports
are parts of a computer that can be used to connect other input/output and
memory devices to it.
Different types of
devices require different types of ports. Ports enable information to flow from
our towards a computer.
E.g.,
A) A serial port is used to connect a computer to a printer or mouse
A) A serial port is used to connect a computer to a printer or mouse
B) A parallel port is
used to connect a computer to a monitor
A)
Serial Port
A serial port is a
general-purpose interface that can be used for almost any type of device,
including modems, mice, and printers.
Serial Port in a Computer
is the one with the symbol IOIOI
Male and Female
Connectors and Wire for Serial Port
B)
Parallel Port
A parallel port is a type
of interface found on computers (personal and otherwisE) for connecting
peripherals. In computing, a parallel port is a parallel communication physical
interface. It is also known as a printer port or Centronics port.
The picture below shows
the image of a Parallel and Serial Port in an old Laptop
Scanning and Data
Interfacing Technologies/Measurements
OCR: Optical Character Recognition
MICR Code: Magnetic Ink Character
Recognition Code
QR Code: Quick Response Code
MIDI: Musical Instrument Digital
Interface
HSSI: High-Speed Serial Interface
HDMI: High-Definition Multimedia
Interface
IOPS: Input/Output Operations Per
Second
USB: Universal Serial Bus
