Computer Hardware:-
Computer Hardware refers to the physical component of a computer that can be seen and touched by the user. By the use of this hardware devices, it made very easy for the computer for processing its data and store and retrieve. Hardware is one of the basic and necessary parts of a computer system.
Input Devices:-
Input devices can be defined as an electro chemical device that allows the user to feed data into the computer for analysis and storage and to give commands to the computer system. The data is entered into the main memory through the input devices. They accept instructions from the user and convert the accepted instructions into the machine language.
Some of the commonly used input devices are:-
Keyboard, mouse, trackball, joystick, light pen, touch screen, barcode reader, OMR, OCR, MICR, smart card reader, biometric sensor, scanner, mic, web cam, PC card etc.
1.Keyboard:-
Keyboard is one of the most common input devices. The user can type text and command using this device. The layout of the keyboard was borrowed from regular typewriter with some additional keys. It is used to enter data or information in a computer, which may be in numeric, form or alphabetic form. When a key is pressed, the keyboard interacts with a keyboard controller and keyboard buffer.
Keyboard controller stores the code of pressed key in keyboard buffer. There are different types of keyboard such as QWERTY, DVORAK, AZERTY.
Types of keys on Keyboard:-
The keys are categorised under the following groups:-
i. Alphanumeric Keys:- It include the alphabet keys(A,B,C ,..., Z) and number keys(0,1,2,..., 9).
ii. Numeric keys:- These are located at the right hand side of the keyboard. They consists of digits and mathematical operators.
iii. Function keys:- These are the programmable keys, i.e. the programs can assign some specific actions. They are numbered from F1 to F12.
iv. Cursor Control keys:- It include four directional(left, right, up, down) arrow keys that are arranged in a inverted T information between the alphanumeric and numeric keys.
There are four more keys to control the cursor.
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These are as follows:-
1. Home:- It is used to return the cursor to the beginning of the line or the beginning of a document.
2. End:- It moves the cursor to the end of the line.
3. Page Up:- When this key is pressed, the page view will be moved up one page and cursor goes to the back page.
4. Page Down:- When it is pressed, the page view will be moved down one page and cursor goes to the next page.
5. Other keys:- A keyboard contains some other keys are as follows:-
a. Control keys:- It performs a special operation with the combination of other keys.
b. Enter key:- It is used to finish an entry and begin the new entry in a document. Enter key is an alternative to press ok button.
c. Shift key:- Some keys on the keyboard like numeric keys have a symbol printed on their upper portion. Shift key is used to print these symbols.
d. Escape key(Esc) :- It allows a user to cancel or abort operations, which are executing at present. It opens start menu with the combinations of Ctrl key.
e. Backspace key:- It is used to erase anything typed.
f. Caps Lock key:- It is used to type the alphabet in capital letters. It enables or disables all the letters from being typed in capital letters. When this key is enable, the alphabet would be in capital letters and when it is disabled, the alphabet would be in small letters.
g. Delete key:- It is used to erase information from the computer's memory and characters on the screen.
h. Num Lock key:- It is used to enable and disable the numeric keyboard.
viii. Windows key:- It is used to open the Start menu.
ix. Spacebar key:- It provides a space between two words. It is the longest key on the keyboard.
x. Tab key:- It is used to move the cursor over to the right to a pre-set point. In Word document, tab is used to indent a paragraph.
Notes:-
- QWERTY keyboard contains total 104 keys.
- Caps Lock and Num Lock keys are called as "toggle keys" because when pressed, they toggle or change their status from one state to another.
- Shift, Ctrl, and Alt keys are also knows as modifier keys.
Pointing Device :-
A Pointing device is used to communicate with the computer by pointing to the locations on the monitor. Movements of the pointing device are you echoed on the screen buy moment of the pointer. Some commonly used pointing device to our mouse, trackball, joystick ,light pen touch screen etc. which are described below:-
1. Mouse :-
Mouse is a small handheld device having two buttons on its upper side and also has a small wheel between these buttons. It is a pointing device which provide a means to input data and commands in graphic form by selecting through moving an arrow called pointer on monitor. The mouse may be used to position the cursor on screen move an object by dragging or select an object by clicking mouse was invented by Douglas Engelbart at Stanford Research Center in 1963.
There are three types of mouse as follows :-
1. Wireless Mouse
2. Mechanical Mouse
3. Optical Mouse
There are four actions of mouse as follows:-
1. Click or Left click :- It selects an item on the screen.
2. Double click :- It is used to open a document or program.
3. Right-click :- Right click displays a list of commands on the screen. Right clicking is used to access the properties of collection object.
4. Drag and Drop :- It is used to move an item on the screen.
2. Trackball :-
Trackball is another pointing device which is an alternative to a mouse. Trackball is also used to control cursor movement and actions on a computer screen. It is generally built in laptop, since there is no space for the mouse on the laptop that ball is used to CAD/CAM workstation and sometimes seen on computerized special purpose workstations such as radar consoles in an air traffic control room and Sonar equipment on a ship or submarine.
3.Joystick :-
Joystick is a device that moves in all directions and controls the movement of the cursor. Joystick are used in flight simulators CAD/CAM system etc. A joystick is similar to a mouse except that the movement of cursor on screen stops working as soon as user stop moving the mouse, but with the joystick the pointer continue moving in the previously pointing direction. Joystick allows movement in all direction (360 degree).
4. Light Pen :-
Light Pen is a handheld electro-optical pointing device used for making drawing graphic and for menu selection. The pen contains a photocell in a small tube. It senses the light from the screen when it become closer and generates a pulse. It is used to especially in Personal Digital Assistant (PDA). It is very useful in identifying specific location on the screen. However it does not provide any information when it held over a blank part of the screen.
5. Touch Screen :-
Touch Screen is an input device that accepts input when the user places of finger on the computer screen. Touch screens have an infrared beam that criss-cross the surface of the screen. The ability to interact directly with a display typically indicates the presence of a touchscreen. Touchscreen is generally used in applications like ATM, Hospitals, Airline reservation and Super market etc.
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