Jelena Mamčenko Operating Systems Lecture Notes on Operating Systems 24 Device Names Character oriented devices can be addressed by DOS through their names: • CON: The name for the video display and keyboard. • AUX: or COM1: This is the first asynchronous communications port which usually has a modem or other serial device connected to it. The second communications port is COM2: • PRN or LPT1: The first parallel printer port. PRN comes from printer and LPT is an old designator derived from line printer. A colon on PRN and all device names is optional in later DOS versions. The second parallel port is LPT2: • CAS1: A holdover; this is the cassette recorder port. • NUL: This is a test device. Anything sent to device NUL: goes into the bit bucket (i.e., gets thrown away). Rules for Filenames Like devices, disk files have to be identified so DOS can address them. These filenames have specific rules. The basic form of a filename is:
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