Input Output Devices and theirTypes
We use a term GIGO for computer, Garbage In Garbage Out. It means that the output of the computer depends upon the input. Out put of the computer depends upon the input data and instructions given to it.
We
use computer simply for some kind of calculations. For calculations we require
some instructions given to the computer hardware to execute the desired task.
The instructions given to the computer hardware are considered as input.
The
devices that are used to enter data and instruction into the computer are
called input devices. The input device is a hardware component. It takes input
(data or instruction) from user and converts it into a form that is
understandable by the computer.
Keyboard is the most commonly used input device. It is mostly used to enter text and numeric type data into the computer. Keyboard looks like a typewriter keypad. But a computer keyboard has some special keys used to perform some special functions. The buttons on the key board are called keys. The keyboard contains keys for all alphabetic characters, numeric digits, and special characters. It also contains some special keys known as function keys. A standard keyboard used in personal computer contains more than 100 keys. The standard keyboard is also referred as QWERTY. This is because the first six leftmost keys on the top row of alphabets are Q,W,E,R,T and Y.
Parts of Keyboard
These are:-
(i)
Function Keys
(ii)
Main Keyboard
(iii)
Numeric Keyboard
(iv)
Additional Keyboard
There are 12 function keys on the top of keyboard that are labeled as F1,F2,…………, F12. These keys provide easy way to give certain commands to the computer. The function of each function key depends upon the software being used on the computer. For example, in many software, the function key F1 is used to get help about the software currently running on the computer.
Main Keyboard
The main
keyboard is like a typewrite keypad. It includes alphabetic character keys,
numeric keys, numeric keys and some special commands keys. The functions of
commands key depend upon the software being used on the computer some the most
commonly used key are:-
Esc Usually, this key is used to cancel the current
action that is being performed
on the computer.
Tab It is used t
insert a tab(space of 6 or 8 characters) into a document from the current position of cursor.
Caps Lock It is used to change lowercase letters mode
to uppercase and vice versa.
The numbers and symbols are not affected.
Shift It is used to type some
uppercase letter if you are typing in lowercase mode and vice versa. Similarly some
keys have two symbols printed on them.
By default, lower printed symbols or letter is typed. To type, the upper case
symbol, the shift key is pressed in conjunction with that key.
Ctrl It is used in conjunction (or
combination) with other keys to apply commands
as specified by the software. For example, in many applications Ctrl + S shortcut
is used to save the current document.
Alt It is also used in combination with other keys to
apply commands as specified
by the software. It can perform some actions stand alone.
Backspace Backspace is used to delete a character to
the left of the cursor. The cursor moved one position backward after
deleting the character.
Enter Enter key is used to insert new
line or paragraph into a word document (or any
text editor). It is also used to perform a selected command or action.
Numeric Keys
This part of keyboard consists of numeric keys and arithmetic operator
keys. These keys are usually located on the right of the keyboard. These keys
are similar to calculator keys. This part of keyboard also has an extra Enter
key and Num Lock key. The Num Lock key is used to activate or de-activate the
numeric keypad.
Additional Keys
Additional keyboards also have some additional keys. Most of these keys
are used to move the cursor inside the document, these keys are:-
Arrow Keys
These keys are used to move the cursor left, right, up and down on the
screen or in the document. These keys are also available in Numeric keys area
as discussed above.
Insert, delete, Home, End, Pg
Up, Pg Down
These keys are also used for the same purpose as discussed in numeric key
area.
Print Screen
This key is used to print the information on the current screen. In
Windows environment, contents of current screen are copied into the clipboard
by pressing this key.
Scroll Lock
This key is used to lock or unlock the scrolling of text on the screen.
When the computer is in the Scroll Lock mode, the status light under “Scroll
Lock” lights up.
Pause
In most of cases, the output of program is appearing very fast on the
screen. In such cases, Pause key is used to pause or stop the information
appearing on screen for reading.
A mouse (mechanical mouse) has a
small ball at its bottom. The ball rotates as the mouse is rolled over a flat
surface. Normally, a pad (also known as mouse pad) is used at flat surface. As
the mouse is rolled over the flat surface, the pointer moves on the screen. The
mouse also has two or three buttons on its top. Usually, mouse is used to
select any icon or option by pointing the mouse pointer on it and clicking one
of the buttons of the mouse to perform an action.
Now days, optical mouse is used with
some PCs. It has no ball at its bottom. It used the laser technology to detect
the mouse movement.
However, a trackball has additional buttons whose functions vary depending upon the software. The trackball is usually available with laptop computers. It is fixed on its keyboard. The laptop computers are used by the users having lot of traveling. The trackball fulfills the needs of those computer users that have no flat surface to roll the ordinary mouse.
Touch Pad Touch pad is a pressure sensitive pointing device. Touch pad is also known as track pad. It is also stationary device like trackball butt it has no moving parts. It is a small, flat surface (sensitive pad) over which we slide our fingertip to move the pointer on screen for pointing a desired icon or item on the screen on the monitor.
As we move our finger on the flat surface of touch pad, the pointer or cursor moves on the screen. Some touch pads have one or more buttons. These are adjacent to the pad. These buttons work like mouse buttons. Touch pads are now commonly used with the portable computers (laptops) and are built in on their keyboards.
Pointing Stick A pointing stick is a pressure sensitive pointing device. It looks like a pencil eraser. It exists between the alphabetical keys G, H and B of keyboard. It is also used to control the movement of a pointer on the screen. The pointer on the screen moves in the direction in which the pointing stick is pushed.
There are also one or two buttons under the spacebar key of the keyboard. A command or an option on the screen is selected by pointing the pointer on it and pressing one of the buttons with thumb. Point stick input device is normally used with laptop computer during some previous years.
Joystick Joystick is also a pointing device. It consists of a vertical handle like a gearshift lever mounted on a base and with one or two buttons. The vertical handle or handheld stick is used to control the movement of pointer on the screen.
The button of the joy stick is pressed to activate certain event or action. The joystick is basically used to play video games. It is also used in some computer aided design CAD systems.
Touch Screen A touch screen is a special video display screen. Input is given to the computer directly by touching the screen with user fingertip. Most touch screen computers use sensors in the computer’s screen to detect the touch of a finger. Usually touch screen is used to make selection from a menu of choices displayed on the screen. Touch screen is often used in ATM. Touch Screen systems are also used in restaurants, supermarkets, departmental stores etc.
The
data after processing becoming into a useful form is called output. The user can receive output from the computer
on a screen or print on the paper through printer. In case of audio output,
then it can be received through speaker. The processed data is also known as
output.
The output deceived on the display screen is called softcopy output. The output in the form of audio or video is also softcopy output. This kind of output is intangible. It means that softcopy output cannot be touched. The most popular and commonly used softcopy output device is display screen and speaker. It is also considered as electronic data.
HARDCOPY OUTPUT
The output printer on the paper is called hardcopy. It may be in the form of text and graphs. The output devices printers and plotters are used for this purpose.
OUTPUT DEVICES
A
hardware component which is used to receive the output from the computer is
called an output device. It takes information from computer and converts it in
a form that is understandable by the users. A lit of commonly used output
devices is as follows.
Printers
Plotters
Speakers
Display screen is commonly used output device. It is used as softcopy
output device. The output may be in the form of text, graphics and video. It
also helps the users to input correct data into the computer and make changes
to the data in computer easily.
It helps the user to manipulate the data in easy way. Display screen is
also referred to as monitor or simply screen.
There are different types of display screens. Display screens are characterized according to the following parameters.
Size
Color
Size
Size of the display screen matters like television screen. The size of display screen or monitor is measured diagonally in inches. For example, a 17-inch monitor measures 17 inches from the lower left to the upper right corner. Display screens are available in various sizes such as 15,17,19,21 and 22 inches. The large size monitors are more expensive and allow you to view more information on the screen at the same time.
Color
Today, most of the display screens show output in multiple colors. The
commonly used display screen is the RGB screen. RGB stands for Red, Green and
Blue. RGB display screen can create 256 different colors and thousands of
variations of these colors.
Some display screens show output in single color. These display screens are known as monochrome screens. These screens are rare in current environment.
Resolution
The display screen is divided into small
dots. These dots are called pixels. The pixels are arranged horizontally and
vertically. The number of pixels on a screen is called its resolution. The
monitor’s screen that has large number of pixels has high resolution. The
resolution means the sharpness and clearness of an image.
We divide printers into different categories depending on their printing mechanism. Therefore, printers are classified into two main categories. These are:-
1.Impact Printer
2.Non Impact
Printer
- Impact Printers
The
printers that produce output on paper with striking the paper are known as
impact printers. Impact printers work like typewriter. They print characters
and graphics on the paper by striking of print hammer or wheel against an inked
ribbon. The image of the characters or graphs is created on the paper. The
examples of impact printers are:-
Dot Matrix Printer.
Daisy Wheel Printer.
Line Printer
- Non Impact Printers
The
printers that product output on paper without striking the paper are known as
non impact printers. These printers are faster and produce high quality output
than impact printers. They are electrostatic, inkjet, and thermal technologies
for printing.
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