Output device is hardware device which is very important part of Computer for example monitor, printer, sound, projector etc.  Monitor is used in every Computer to display picture and Printer is used for printing documents. Any computer cannot work without hardware device you'd have idea to find out what the computer is doing if show some technical errors, or if it required some other function keys. For example, if you are not using monitor from your computer then you cannot run any function. For more information check out what is Output Device in Hindi.