Input Devices
The function of Input units of a Computer is
to feed data into the memory of CPU. The Data to be processed is fed into the
computer through these input units. Ther are a number of different types of
input units out of which we can choose the appropriate ones needed to
facilitate this process of data input.
Input Device Consist:
· Mouse
· Magnetic Ink Character Recognition (MICR)
· Optical Character Recognition (OCR)
· Optical Mark Reader
· Scanner
· Light Pen
· Bar code Reader
1. Keyboard
The keyboard
is an Input or peripheral device that lets you “communicate” or “talk” to the
Computer. Keys are pressed on the keyboard to tell the Computer what to do.
There are 101 or 104 keys on the standard computer keyboard. Some keys are
still being added in the keyboard for the different reasons.
The user
uses the keyboard to type-in the input for the CPU. This is very similar to an ordinary
typewriter except with one major difference in operation that keyboard keys are
softly pressed compared to typewriter keys. Therefore, it is convenient to work
with the computer for log hours than with the typewriters. One more specialty
about the keys of the keyboard is that if it is kept pressed, it repeats
itself. A modern keyboard is shown in the following figures.
Keyboard is
connected to computer via cable, whose one end is connected to keyboard and the
other is connected to a socket back of the CPU. Compared to typewriter,
keyboard consists of some additional keys, which are used to perform a variety
of jobs. On the top right corner of the keyboard, there are 3 LED indicators,
which show the current status of Caps Lock, Num Lock and Scroll Lock.
All the keys of the keyboard can be classified
into following six groups:
·
Number Keys
·
Alphabets Keys
·
Function Keys
·
Editting Keys
·
Control Keys
·
Symbol Keys
Number
Keys
These keys
are 10 in number and print number from 0-9. These are present on the top of the
middle part of the keyboard.
Alphabet
keys
There are 26
keys on the Keyboard having Alphabets on the keyboard printed on them i.e. that
is from A to Z. These keys are used to print both capital and small letters.
These keys are arranged in the same order as they are present on typewriter.
Function
Keys
There are 12
function keys on the Keyboard Marked from F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11 and
F12. These keys can be assigned a special command functions in different Software.
Editing Keys
There are 13
keys on the keyboard which falls in the editing keys category. They are used to
modify the text on the screen. Some of the editing keys and the specific
functions are detailed below:
Keys Functions
Ó It is used to move the cursor one line
up
Ô It is used to move the cursor one line
down
Ñ
It
is used to move the cursor one column left
Ò
It is
used to move the cursor one column right
Pg Up It
is used to move the cursor one page up
Home It is used to move the cursor to the left
corner of the line
Home It is used to move the cursor to the right
corner of the line
Backspace It moves cursor one space to
the left by erasing a character
Spacebar It is the longest key on the
keyboard, which moves the cursor to the right by erasing the character
Delete/Del It removes /deletes the
character present over cursor, i.e. to . the
right of the cursor
Insert It is used to add
(insert) some text in between 2 Characters
Tab It jumps the cursor
by 5 spaces to the right
Control
Keys
These keys
are used to control the input, output and processing operations of computer.
Following are the Control Keys on the Keyboard.
Keys Functions
Enter /
Return This is the most important key on the
keyboard and it is used to execute the command given to
the Computer. The Enter Key on the
Keyboard is used to tell the Computer to start a
new line.
Shift When the Shift key is pressed, and any alpha key is pressed, its case is changed, i.e. normally
it displays lower case, but with the Shift key it makes it an upper case.
Esc (escape) It is used to interrupt the Computer while processing. This key is used to exit a screen or a program.
Pause It is used to stop Computers temporarily
during processing. When Enter key is pressed, it continues processing.
Caps lock It is a toggle key, which means it
has two values, ‘ON’ or ‘OFF’. When
ON, all alphabets type are taken capital. If typed with shift key, it will become smaller.
Num Lock By
pressing Num Lock, we can activate the Numeric key pad present on the right side of the Keyboard.
Scroll Lock This key is used to stop the information on screen, which is continuously appearing on the screen.
Ctrl(Control) This key does not have its own fixed function, but when pressed with other keys, it performs specific work.
Alt (Alter) Like Ctrl key, this key too does not have any fixed function, but when pressed with other keys, it performs a specific function.
Symbol
Keys
These keys do not perform any function, but when pressed they display special characters. The symbol keys are as follows-
! @ # $ % ^ & * ( ) _ - ` ~ / > < \ [ ] { } ? ; : | = +
2. Mouse
The various parts of the Mouse as follows:
- Left button
This button is used for giving some commands to the computer or generally used for selecting or dragging text and objects.
- Right Button
This button is not frequently used. When you want to perform some shortcut operations, Than you can use the right button. When you presss this button in MS-WORD, it will bring a shortcut menu having some commands to select from.
- Middle Button
This button is rarely used in some applications. It is mostly used in video games or some other Computer based games.
- Ball
Ball is used to move the mouse freely
- Rollers
Rollers control the direction and position (coordinates) of the pointer or cursor on the screen
- Cable
Cable is used to connect the mouse to the Computer.
3. Magnetic
Ink Character Recognition(MICR)
This is
another input device, which is becoming very popular in the banking industry.
The Computer can directly pick up the data from the input forms without any
need to type it at the keyboard of the terminal.
The new cheques
introduced in the banks are known as MICR Cheques. There is a white band at the
bottom of the cheques, which contains some information written with the special
ink. This in contains Magnetized Iron Oxide in it. Thus each character written
can be imagined as a small iron piece, which is magnetized and pasted on the
cheque. The input device can read these characters by sensing these magnetized
characters.
When this
cheque is inserted in the computer, it can read all this detail and allow the
transaction to be processed. The MICR character contains only the number and the
few special characters. It offers a very high reading accuracy. Another
advantage is that the cheque can be read both by machine and the human being.
Advantages of MICR
It’s reading
accuracy is very high
Both Man and
Machine can read the Information.
The speed of
Data Entry is very High.
Disdvantages of MICR
Data
preparation time is very high in this system.
MICR can
read only that information, which is written only in the special font using special ink.
4. Optical Character Recognition (OCR)
It is a technique for reading a the data, which need not
to be written with special ink as in the case of MICR. It can recognize and
pick up the data as well as pictures or images written / drawn in any color
with ordinary ink. The stored Image can then be processed. This processing is
often turned as image processing.
The Reading technique involves illuminating the
characters/picture to be read by a source of light. The reflected light is scanned for picking out a pattern, which can be compared with the standard patterns already, stored with dark / light combinations. This technique employed is known as Pattern Recognition.
Advantages
of OCR
- There is no need to re-prepare
data by users.
- OCR can read both typed or hand
written document.
Disadvantages
of OCR
- It is a very costly system.
- Special font is used to
prepare the source document.
5. Optical Mark Reader (OMR)
This
input device can be used to feed the data for the situations where there are
Pre-defined options for the various parameters for which data is needed.
6. Scanner
Scanner is such a hardware device, which is generally
used to read graphical images from the source documents and entered into
computer for further processing or storage. This system is known as Source Data
Automation. To read data from the source document, scanner scans and digitizes
the data using laser techniques and converts it into the Internal Data
Representation, So that it can be stored in the memory and can be edited.
For the Work Publication Scanner is a necessary device.
7. Light Pen
Light pen utilizes a light-sensitive detector to select objects on a display screen. A Light pen is similar to a mouse except that with a Light Pen you can move the pointer and select objects on the display screen by directly pointing to the objects with pen.
8. Bar Code Reader
Data coded in the form of light and dark lines of bars are known
as Bar Code. Bar Code Reader is a device used for reading (decoding) bar code
data. Bar code reading is performed by a laser-beam scanner, which is linked to
a computer. The laser beam is stroked across the pattern of bits that is
recorded as the input data.
Writer: Mr Krishan Kumar Saini
Today we have learnt about the Input Device of Computer. Hope this lesson is helpful for you.
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