Chapter Input devices

INPUT DEVICES

 

Input devices is a device through which we feed data into the computer.When data are entered in the form of digits, alphabets and other special character, input devices converts it into their respective codes to be used by computer.There are many input devices which can be used for inputing data with different computers.Some are described below:

KEYBOARD

The most common input device is a keyboard which look like a typewriter. But it has some extra keys to perform some special tasks.There are function keys, cursor control keys and some special keys.All the keys of a keyboard can be classified in different categories as follows:

Alphabet keys

These are represented by alphabets from A-Z and are used for entering alphabets.

Numeric keys

These keys are the keys on the second row of the keyboard from the top having digits from 0-9.There are some symbols marked on the top of each digit.These symbols are :

~ , ! , @, #, $, %, ^,&,*,(,),-,+,\
If you want to display any of the above symbols,you will have to press shift key along with the desired symbol.
A second set of number keys are on the right corner.These number keys are used to feed mathematical data conveniently.

Cursor control

There are four arrow keys on the right hand side of the keyboard.They move the cursor in the desired direction.They are also used to move the selected text or object to the desired location on the monitor.
Besides these arrow keys, there are some more keys which are used to control cursor.These keys are tab, space bar , Home , End etc.

Function keys

These keys are also called user defined keys because function of these can be defined by the user according to his requirement.They have different programs.These keys are on the top of the keyboard and are marked with F1,F2…………F12.

Special keys

These are several special keys on the keyboard.These keys perform special operation depending upon the characters with they are used.Some of the special keys are as follows:

(a) Alt : These are two such keys on the keyboard.This is also called ‘alternate ‘ keys. It has no function when pressed alone.But when pressed with another key or keys it generate some effect.

(b) Ctrl : It also have no effect when pressed alone but when pressed along with one or more keys, it becomes functional. It is also two in numbers on the keyboard.

(c) Shift : It is used to type capital letters.When this key is pressed along with any other alphabetical key, it produce capital letter.It works differently when caps lock is on.There are two shift keys on a keyboard.

(d) Tab : It moves the cursor in desired steps.(for greater spacing then spacebar produce)

(e) Caps lock : It is a toggle key which means like a switch.When we press this key a indicator top right corner shows that the key is working and when we press it again it gets disabled.It is used to write alphabets in capital letter.

(f) Enter : It is a very important key of a keyboard.This key is used to execute the desired command. We press this key after selecting the command.This key is also used to bring the cursor on a new line.

(g) Backspace : This key is used to delete character from the left side of the cursor.

(h) Del : This key is used to delete character from the right side of the cursor.

(i) Esc : This key is called escape key. It is used to escape from the executing command.

(j) Num lock : This key is pressed to make enable digits of Num pad operating in the right side of the keyboard.

MOUSE

Mouse is also an important input device and it also known as a pointing device.It has a hard rubber ball in its bottom.When a mouse is scrolled on a mouse pad, the pointer or cursor also moves over the monitor.
There are two or three buttons which can be used to execute commands.It is easier to select a command with the helps of mouse rather than selecting by keys.

SCANNER

Scanner is also an input device which works same as a xerox machine.It is used to input pictures and photographs into the computer directly.There are mainly two types of scanners:
(i) Hand-Held scanner
(ii) Flatbed scanner
Hand held scanner is small in size so that can be held in one hand.This scanner is used to copy small size of images like logos, signatures etc. Flatted scanner is comparatively big in size.It is used to input an entire page into the computer.You can edit and modify the scanned pictures on a computer with the help of software.

JOYSTICK

Joystick is an interesting input device.It is used to play games in computer.It allow user to move an object on the screen.
A joystick is a stick set in two grooves.This stick can be moved in any direction over the screen. The movements are converted into binary instructions with the help of electrical contacts in its base. A joystick controls the velocity of the screen cursors movements.

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