CS-Input _Output_Devicesx 1291KB Nov 27 2012 06:09:22 AM

agreementkittensSemiconductor

Nov 2, 2013 (3 years and 7 months ago)

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is any
hardware
that takes
input from
the user.


Enters data into computer by pressing one key
at a time.



STRUCTURE


Alphanumeric Keys :
(A
-
Z),(0
-
9),(+,
-
,*,/)


Numeric Keypad :
(0
-
9) on right hand side


Function Keys :
F1


F12


Cursor Movement Keys :

,

,

,




When user press a key on keyboard, a tiny computer chip
called
Keyboard Controller
, records that a key has been
pressed.


Keyboard Controller places the code into a part of
memory, called
Keyboard Buffer
, indicating the key has
been pressed.


This code is called
Key’s Scan Code.


Then keyboard sends an
Interrupt request

(special
message to computer system in form of signals) to the
system software when it receives a complete key stroke.


When system software receives an interrupt request, it
evaluates the request to determine an appropriate
response.


It passes the scan code to CPU then.


ADVANTAGE


Faster in entering data than in positioning
devices.


More reliable and produce fewer error than
others.

DISADVANTAGE


Take a lot of time in practice to type quickly.


Typing speed is still very slow when
compared with computer speed.


MOUSE


Pointing device that translates the motion of
mouse into signals.



Two rollers are placed attached to the mouse
ball exactly at 90 degree to each other.


When mouse ball rotates, rollers also rotate.


On either side, there is an
infrared emitter
and
on board chip read pulses (signal) from
infrared sensors turns them into binary data.

DRAWBACK


Performance Degradation like ball takes dust
and obstructs proper motion of shafts.



It uses small camera that takes 1500 pictures every
second.



Light Emitting diode (LED) bounces off light of
surface onto Complementary Metal Oxide
Semiconductor (CMOS) Sensor.



CMOS sends each picture to digital to see how the
image has changed since previous change.


The Digital Signal Processor operates at 18 million
instructions per second.



By analyzing these images, processor determines the
movement of cursor on screen.


ADVANTAGES


User friendly for computer beginner.


Easy and convenient to use GUI.


Selection and movement on screen is faster
than using keyboard.

DISADVANTAGE


Not easy and convenient to input text.


Issuing command is slower than keyboard.


Needs practice.


Requires flat screen to operate.


It is handheld input device that contains a light
source or can detect light.




Light Pen contains a lens that focuses light
from computer monitor onto photoelectric
cell.


As monitor’s electron beam passes through
lens, cells emit an electric pulses.


Strengthen by an amplifier, pulse is sent as
digital signal and computer determine
location of pen on screen.


A touch of light pen’s control button tells
computer to note this position for selection.


ADVANTAGE


More direct and precise than mouse.


Convenient for application with limited
desktop space.


DISADVANTAGE


It requires special designed monitors.


A monitor that has a touch sensitive panel on
screen.



You interact with the computer by touching
areas of screen with fingers that acts as input
device.




Whenever user touches the screen, it disturbs
the electrons emitted on screen and
computer processor recognizes the area
where the electron are being damaged and
considers it as selection.


ADVANTAGE


No extra peripherals are needed except
monitor.


It allows easy access on commands.

DISADVANTAGE


It is not suitable for inputting a large amount
of data.


Only items already on screen can be
detected.



An input device which translates paper
document into an electronic format, which
can be stored in computer. The input
document can be text, picture, graphics.


Types of Scanner

1.
Flatbed scanners

2.
Handheld scanner

Like a copy machine, this consists of a box having
a glass plate on the top, and a lid that cover the
glass plate.




WORKING

The document is to be scanned is placed upside
down on glass plate. Light source below plate
moves horizontally from left to right. After
scanning one line, light beam moves up a little
and scan next line and process repeats for all
lines.


It has set of LEDs placed in a small case, which
conveniently held in hand during operation.

WORKING

To scan a document, a scanner is slowly
dragged very steadily and carefully over
document.


Is any
hardware
component
that can
convey
information
to user.



It’s the most important output device


2 common types


CRT


LCD


Featured by:


Refresh rate


Resolution


Visible screen size


Response time



CRT monitors a CRT is used as the picture of monitor. The screen is
divided into rows and columns. Each cell of this screen is called
Pixel.




This vacuum tube contains a negatively charged cathode which
shoots electrons at the back of positively charged screen.




The screen is coated with phosphorous chemical.



When the electrons strike the back of the screen, phosphorous is
excited and it provides a glow to individual pixels.



The distance between these pixels called as
Dot Pitch
and it is
measured in millimeters.



The picture tube redraws the picture after a short interval. The
number of times the electronic gun redraws the picture on screen
is called as the
Refresh Rate

and it is measured in Hertz(Hz).



The number of pixels per unit area of the screen is called as
Resolution.

More the resolution, more clearer will be the picture.



Higher refresh rates.



Ability to adjust images.



Display full motion video better.



Significantly lower cost because the technology
has matured.



Work better at multiple resolutions.



Modern version may include a sleep mode for
energy efficiency.



Color fidelity, so essential for graphic artist, has
not been matched by LCD’s.



Screen images viewed from side angle are as
good as when viewed straight on.



Larger size takes up more desk space, the
bigger the screen, the bigger the foot
print.



Heavy weight.



Heavier size limits easy and convenient
movement.



Expands more energy and throws off heat.


FLAT PANEL
DISPLAYS

EMISSIVE

PLASMA
PANELS

LED
PANELS

NON
-
EMISSIVE

LCD



Plasma is often
called as forth
state of matter
other three being
solid, liquid, gas.



Plasma is a
distinct state of
matter containing
number of charged
particle.


Plasma panels are two edge
-
sealed layers of
glass separated by a thin layer of neon based
gas.



There are horizontal conductors on one glass
layer and vertical on the other glass layer.



When the voltage is applied on the
intersection of horizontal and vertical pair of
conduction the gas at the intersection
become ionized and emit a spot light.



All the conductor may have sustaining
voltage applied to them that keeps the spot
eliminated for several thousand times a
second.




LED stands for light
emitting diodes which are
basically used in
calculators, retail
counters, large digital
watches etc.


The first LED’s that were
used deep red in color but
other colors are also
available now.


It is a type of emissive
device.



In this a matrix of diodes is arranged to form
pixel positions in the display.


The picture definition is stored in the frame
buffer.


As in scan lines refreshing of a CRT,
information is read from the refresh buffer
and converted to voltage levels that are
applied to the diodes to produce light
patterns on the display.



The screen used in computer devices is the LCD
screen. The LCD screen produces images by
aligning molecular crystals.



The LCD screen consists of twisted crystals.
These crystals are present in twisted form like a
spring and they untwist at varying angles when
varying voltages are applied.




These crystals are packed in two screens. The
front screen is transparent and back screen is
reflective.




The back screen reflects light towards the
front screen. The light gets deviated by these
molecules.



This backed and deviated light produces
images on front layer.




Light weight.



Smaller foot print on desk leaving, freeing up work
area on the user desk.



Flicker free screen.



More usable display area than on comparably sized
CRTs.



Low frequency radiation is practically eliminated.



Easy adjustment storage and movement.



Efficient energy and they do not generate heat.



Good for basic web surfing.



Potentially less eyestrain due to reduced screen glare.



Fragile screen may result in both screen and
back light lamp damage if touched. Thus not
recommended in environments where it may be
handled roughly



Contrast ratio causes darkness to not be
displayed true. Darkest area may be viewed as
dark grey rather than black



Designed only for optimum resolution, can’t
adjust images



The color accuracy of an LCD monitor does not
match that of a CRT monitors.



These are more expensive than CRTs.



A printer is an output device that produces
text and graphics on a physical medium such
as paper.


Printed information is often called
hard copy
because the information exists physically and
is a more permanent form of output than that
presented on a VDU (Monitor).


Printers can be grouped into
-

impact and
non
-
impact printers
-




An
impact printer
forms characters and
graphics on a piece
of paper by striking a
mechanism against
an ink ribbon that
physically contacts
the paper.



A
non
-
impact printer
forms characters and
graphics on a piece
of paper without
actually striking the
paper.



Speed of printer
-

The printing
speed of a
printer
is usually expressed in pages per minute

(
ppm
).



Resolution
-

Printer
resolution

is often
expressed in dpi (dots per inch). The larger

the
number, the higher the resolution.




Information produced is permanent.


The time to get the printout is
slow, when compared with
display devices.



Paper is wasted for obtaining
the output.



Printers are generally noisier
than display devices.



The print head travels from side to side across the
paper and is made up of numerous pins which are
pushed out to form the shape of each character


The pins hit an ink ribbon against the paper so the
characters are printed out.


The paper is usually continuous with holes down each
side and perforations so the pages can be easily
separated by tearing.


Because the pins make an impact against the paper
the characters can be printed through several layers
of self
-
carbonating paper to produce duplicate copies.



Limited to situations
where duplicate
copies are needed and
the quality is not too
important.


Typical uses might be
in

warehouses

where
duplicate copies of
orders need to
produce quickly and
cheaply.


The

purchase cost is low

and the

running
costs are very low.


They can print

fairly quickly, particularly if
you remember that multiple copies are being
printed in one print run.


They are

robust

and can operate in

harsh
environments.


If several sheets of self
-
carbonating paper are
placed into the printer then the impact will
produce

duplicate copies.


The printing

quality is
low

-

these printers
produce low to
medium quality black
and white printing
and can only print low
resolution graphics.



Because of the impact
of the pins against the
paper, these printers
can be

quite noisy.


An ink
-
jet printer is a non
-
impact printer that
forms characters and graphics by spraying tiny
drops of liquid ink onto a piece of paper. Ink
-
jet
printers can produce letter
-
quality text and
graphics in both black
-
and
-
white and colors.




Some ink
-
jet printers can print photo
-
quality
images on any type of paper. Printer resolution
is measured in dots per inch (dpi). The speed of
an ink
-
jet printer is measured in pages per
minute (
ppm
).



The print head contains tiny nozzles through
which different colored inks can be sprayed
onto the paper to form the characters or the
graphic images.


The ink is forced out by heat or by tiny
piezoelectric crystals which change shape
when an electric current is applied across
them.



A popular choice
for

home use

where
small amounts of
printing are done
and photographic
quality color printing
is needed.


The speed over 150
ppm
.




Inkjet printers are generally quiet.




Inkjet printers can produce high quality color
output.




These printers are

relatively inexpensive





Specialized papers are required to produce
high quality color output.


The

printing speed is slow

compared to a
laser printer.



The ink cartridges and specialized papers are
expensive.


The ink may smear when printed on ordinary
paper.