Serial ports are given the DOS device "COM1:" to "COMx:" in even now in the NT Object Namespace. (Serial MUX boxes & IO Cards can allow a PC to have up to 15 or 25 serial ports per PC. We used to use a large 486 with Minix to run 45 "dumb terminals" via serial ports... In Unix they where /dev/tty0 - /dev/tty44, but if we installed DOS or Windows they would be COM1: - COM45: and base DOS / Windows 3.x wouldn't allow for more than COM9: NT4+ can cope with more, and can use other names, (via, Junction in the Namespace, but COMx: is what the OS sets up by default.
Likewise access to Parallel ports are "LPT1:" and "LPT2:"... I have had a PC with 2 IO boards giving 3 parallel ports, but couldn't ever allocate an LPT3: symbolic link in the namespace, but DOS and the "IBM Compatible" BIOS won't allow for the resources (IRQ and IO ports) for more than 2 parallel ports.
"PRN:" is allocated to the default COM, LPT or USB port on which the default printer is connected... both in DOS and (for backwards compatibility) in the NT Object Namespace.
Under DOS "CON:" refers to the default console / text mode output device where StdOut and StdErr are redirected from you C programs. A new one is mapped for each DOS window under the NTVDM (NT - Virtual DOS Machine).
You could "Subst PRN LPT2:" to use parallel port 2 (instead of port 1) as the default printer. Likewise you could "Subst CON COM1:" and attach a similar "dumb terminal" (teletype device, hence the unix name "tty", now "ttys0" - "ttys9" for the screen attached to the PC) to your serial port, and control DOS (or the NT command line) from that. You can attach a second PC via a 4-5 cross RS232 cable to your first and connect to such a "redirected" console via a Virtual Terminal program... one still ships with Windows OS. XD
Under NT, you can also redirect those ports to TCP/IP ports on your internet connection.
I respectfully suggest that this is protection against an attack... similar to the way you check for SQL commands in user names and password fields in registration pages.
You can read how NT maps the DOS device names we are still used to using (C:, D:, COM1:, LPT1: etc) from the true namespace name
You must be registered to see links
. You will find that explorer will navigate to directories via "//./" NT namespace paths just as well as the "old DOS" paths we still cling to.
There was some upset when they tried to remove drive letters from Vista "Home Server" Edition, but it really is an antiquated method of working... and NT is much more powerful than 24 lettered "drives". So we can blame "Windows users" (not Microsoft) for it's continued existence. MS have a fantastic OS, but most of the useful stuff is hidden because (despite what they say) it seem most people just want DOS to run more programs faster. <shrugs>
