Input device used in computer system:

An input device is typically a mouse or keyboard, the input device is the conduit through which data and instructions enter a computer. A personal computer would be ineffective if you could not interact with it due to the machine could not receive instructions or deliver the results of its work. Input devices accept instructions and data from the user or from another computer system (such as a computer on the Internet). Output devices   return processed data to the user or to another computer system.

The most common input device is the keyboard, which accepts numbers, letters and commands from the user. Another essential type of input device is the mouse, which lets you select choice from on-screen menus. One uses a mouse by moving it across a flat surface and pressing its buttons. A range of other input devices work with personal computers, too: The touchpad and trackball are variations of the mouse and enable you to choose, draw or point on the  screen. The joystick is a rotating lever mounted on a stationary base that is fit for playing video games.