Device files are yet another feature that was kludged into MS-DOS in a half-assed attempt to emulate UNIX.

Where Linux (The only Unix-like OS that I'm familiar with) has hundreds of devices, DOS has 9.

• CON: The video display (or DOS window, under Windows) and keyboard. Similar to /dev/tty's under Linux.
• LPT1 or PRN: The first parallel port, generally the printer.
• LPT2, LPT3: Parallel ports 2 and 3, respectively.
• COM1, COM2, COM3, COM4: Serial ports.
• NUL: the empty bit bucket. Equivalent to Linux's /dev/null