Reserved word

Updated: 11/16/2019 by Computer Hope

A reserved word may refer to any of the following:

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 another service. Below is a listing of Microsoft reserved words in MS-DOS and Windows operating systems. When attempting to use any of the following reserved words as a file name or command, you may receive an error message. 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 Console, which Microsoft describes as the display monitor or keyboard.
COM1 COM port
COM2 COM port
COM3 COM port
COM4 COM port
LPT1 LPT port
LPT2 LPT port
LPT3 LPT port.
NUL NULL
PRN Printer aka LPT1

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