I have to confess that I am puzzled about all the talk about 4 serial
ports.

If you have a modem you get a fast port built in with that.  Most machines
come with two ports as standard.
My PIC programmer uses the parallel port.  My mouse uses Com1.  My modem
uses Com4.  I have no Com3 but that is no problem.  I have Com2 free for
any plug in serial devices (usually PIC based).

Why all the hassle about a 4th port I ask myself ????

TTFN  -  Peter.