Introduction:-

Any piece of hardware that transmits data to a computer, enabling interaction and control, is referred to as an input device. An example of an input device is the Logitech trackball mouse in the image. The keyboard and mouse are the two basic input methods used by computers. However, a computer can also be fed data from other sources. 



Keyboard:-

                        The most commonly used input device is a keyboard. The data is entered by pressing the set of keys. All keys are labeled. A keyboard with 101 keys is called a QWERTY keyboard. The keyboard has alphabetic as well as numeric keys. Some special keys are also available. 1.Numeric Keys: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 2.Alphabetic keys: a to z (lower case), A to Z (upper case) 3.Special Control keys: Ctrl, Shift, Alt 4.Special Symbol Keys: ; , " ? @ ~ ? : 5.Cursor Control Keys: ↑ → ← ↓ 6.Function Keys: F1 F2 F3....F9. 7.Numeric Keyboard: It is on the right-hand side of the keyboard and used for fast entry of numeric data.

Function of Keyboard: 

                                    1. Alphanumeric Keyboards are used in CAD. (Computer Aided Drafting).

                                    2. Keyboards are available with special features line screen coordinates entry,                                                Menu selection or graphics functions, etc. 

                                    3. Special purpose keyboards are available having buttons, dials, and switches.                                             Dials are used to enter scalar values. Dials also enter real numbers. Buttons                                               and  switches are used to enter predefined function values.

 Advantage:

                      1. Suitable for entering numeric data. 

                      2. Function keys are a fast and effective method of using commands, with fewer errors.

 Disadvantage: 

                      1.Keyboard is not suitable for graphics input. 

Mouse:

                  A Mouse is a pointing device and used to position the pointer on the screen. It is a small palm size box. There are two or three depression switches on the top. The movement of the mouse along the x-axis helps in the horizontal movement of the cursor and the movement along the y-axis helps in the vertical movement of the cursor on the screen. The mouse cannot be used to enter text. Therefore, they are used in conjunction with a keyboard. 

Advantage: 

                        1.Easy to use 

                        2.Not very expensive 


Light Pen:-

                  • Light Pen (similar to the pen) is a pointing device which is used to select a displayed                               menu  item or draw pictures on the monitor screen.
                  • It consists of a photocell and an optical system placed in a small tube. 
                  • When its tip is moved over the monitor screen, and pen button is pressed, its photocell                             sensing element detects the screen location and sends the corresponding signals to the                             CPU.

Uses: 
         1.Light Pens can be used as input coordinate positions by providing necessary arrangements. 
         2.If background color or intensity, a light pen can be used as a locator.
         3.It is used as a standard pick device with many graphics system.
         4.It can be used as stroke input devices.
         5.It can be used as valuators 


Touch Panels: 

                       • Touch Panels is a type of display screen that has a touch-sensitive transparent panel                                  covering the screen. 
                       • A touch screen registers input when a finger or other object comes in contact with the                              screen. 
                       • When the wave signals are interrupted by some contact with the screen, that located is                             recorded. 
                       • Touch screens have long been used in military applications. 


Graphic Tablet:

                         • A graphics tablet or digitizing tablet, graphics pad, drawing tablet is a computer input                              device that allows one to hand-draw images and graphics, similar to the way one                                      draws images with a pencil and paper.

                         • A graphics tablet consists of a flat surface upon which the user may “draw” an image                               using an attached stylus, a pen-like drawing apparatus. The image generally does not 
                           appear on the tablet itself but, rather, is displayed on the computer monitor.



 Below is a list of professions and people who are more likely to use a graphics tablet.

 •Architects and Engineers 
•Artists 
•Cartoonist 
•Fashion designers 
•Graphic designers 
•Illustrators 
•Photographers 
•Teachers 


Joystick: 

              • A Joystick is also a pointing device which is used to change cursor position on a monitor                         screen. 
              • Joystick is a stick having a spherical ball as its both lower and upper ends as shown in fig.



                    • The lower spherical ball moves in a socket.
                    • The joystick can be changed in all four directions. 
                    • The function of a joystick is similar to that of the mouse.
                    • It is mainly used in Computer Aided Designing (CAD) and playing computer games.