This is a ball which is half inserted and by moving fingers on the ball, the pointer can be moved. Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse. When the tip of a light pen is moved over the monitor screen and the pen button is pressed, its photocell sensing element detects the screen location and sends the corresponding signal to the CPU. It consists of a photocell and an optical system placed in a small tube. It is used to select a displayed menu item or draw pictures on the monitor screen. Light pen is a pointing device similar to a pen.

It is mainly used in Computer Aided Designing (CAD) and playing computer games.

The function of the joystick is similar to that of a mouse. The joystick can be moved in all four directions. The lower spherical ball moves in a socket. It is a stick having a spherical ball at its both lower and upper ends. Joystick is also a pointing device, which is used to move the cursor position on a monitor screen. Moves the cursor faster than the arrow keys of the keyboard.A mouse can be used to control the position of the cursor on the screen, but it cannot be used to enter text into the computer. Generally, it has two buttons called the left and the right button and a wheel is present between the buttons. It is a very famous cursor-control device having a small palm size box with a round ball at its base, which senses the movement of the mouse and sends corresponding signals to the CPU when the mouse buttons are pressed. Mouse is the most popular pointing device. Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen. Control keys also include Home, End, Insert, Delete, Page Up, Page Down, Control(Ctrl), Alternate(Alt), Escape(Esc). These keys provide cursor and screen control. Each function key has a unique meaning and is used for some specific purpose. The twelve function keys are present on the keyboard which are arranged in a row at the top of the keyboard. Generally, it consists of a set of 17 keys that are laid out in the same configuration used by most adding machines and calculators.

It is used to enter the numeric data or cursor movement. These keys include the letter keys (A-Z) and digit keys (09) which generally give the same layout as that of typewriters. The keys on the keyboard are as follows − S.No Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet. The layout of the keyboard is like that of traditional typewriter, although there are some additional keys provided for performing additional functions. Keyboard is the most common and very popular input device which helps to input data to the computer. Following are some of the important input devices which are used in a computer −

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