In terms of Serial Ports what does COM actually stand for. I can't find any reference to it.

(To be clear I am not talking about Component Object Model but the Hardware Interface used in Windows Environments)

I assume it is an acronym as it is always capitalised?

  • It's capitalized for historical reasons. At the time, all filenames (and device names) on PCs were always uppercase. If I remember correctly, mixed-case filenames didn't appear until Windows 95. Jun 11, 2012 at 21:11

1 Answer 1


It stands for communications i believe - since parallel ports were lpt (or line printer ports) and serial ports were used for communications.

Interestingly I haven't found any reference that confirms this so far however - this is the closest i can find to a reference, but it seems to be taken for granted in windows and dos. There's no acronym or acronym for COM as far as i can tell

(Interestingly in linux, they are called tty - which refers to a teletype machine)

  • From PCMag - Definition of: COM1 In a PC, the name assigned to the first serial port. The second is COM2, etc. PCs are typically designed to support up to four serial ports. On earlier PCs, two external serial ports were provided to connect a mouse and modem. On newer PCs, there is often only one external serial port as mice use a separate PS/2 port, and modems are generally built in and use an internal serial port. The term originated before the days of the mouse, when the serial port was primarily used for modem COM-munications. Contrast with LPT1.
    – Joe Taylor
    Jun 11, 2012 at 12:46
  • Last line - COM-Munications - more support for the answer.
    – Joe Taylor
    Jun 11, 2012 at 12:46

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