1. A character code with a null value; literally, a character meaning “nothing.” Although it is real in the sense of being recognizable, occupying space internally in the computer, and being sent or received as a character, a NUL character displays nothing, takes no space on the screen or on paper, and causes no specific action when sent to a printer. In ASCII, NUL is represented by the character code 0. See also ASCII.
2. A “device,” recognized by the operating system, that can be addressed like a physical output device (such as a printer) but that discards any information sent to it.