Reserved word

1. Often found in programming languages and macros, reserved words are terms or phrases appropriated for special use that may not be utilized in the creation of variable names. For example, "print" is a reserved word because it is a function in many languages to show text on the screen.

2. Reserved words are used in operating systems as a method of identifying a device file or other service. Below is a listing of Microsoft reserved words in MS-DOS and Windows operating systems. When attempting to use any of the below reserved words as a name of a file, or in a command you may encounter and unusual response. For example, attempting to save a file as CON or CON.txt may generate a reserved file name or access denied error or say the file already exists.

Reserved Word What it is
AUX Auxiliary port aka Serial Port COM1
CON Short for console, which Microsoft describes as the display monitor.
COM1 COM port
COM2 COM port
COM3 COM port
COM4 COM port
LPT1 LPT port
LPT2 LPT port
LPT3 LPT port.
PRN Printer aka LPT1

Also see: Device file, Java reserved words, Operating system terms, Programming terms, Reserved character, Word