A computer keyboard is a device which uses an arrangement of buttons or keys to act as mechanical levers or electronic switches. Keyboard keys typically have a set of characters engraved or printed on them, and each press of a key typically corresponds to a single written symbol. However, producing some symbols may require pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or symbols , other keys or simultaneous key presses can prompt the computer to execute system commands. In a modern computer, the interpretation of key presses is generally left to the software. Normally keyboard is used as a text entry interface for typing text, numbers, and symbols into application software and for playing PC Games.