Six external parts of a computer system are:
Output
1. Monitor
2. Headphones
3 .Printer
Input
1. Keyboard
2. Mouse
3. Video web camera
An output device is a computer hardware equipment which is used to receives data from a computer and converts the electronically generated data into a form that can be read by humans.
An input device is a component or hardware that is used to send or feed data or instruction to a computer for the purpose of processing, storage, display, transmission or outputting. Input devices convert the analog data of the user to digital format that can be processed by the computer.