CHECKIRQ.EXE

This command is entered on the DOS command line as CHECKIRQ. It responds
with a listing of all the COM ports on the computer and their IRQ numbers.
Unlike WHATPORT, this program actually reads and checks the port IRQ and
does not merely assume they'll be standard.

The 4 COM ports on my system show correctly as:

Found COM1, testing...uses IRQ4
Found COM2, testing...uses IRQ3
Found COM3, testing...uses IRQ4
Found COM4, testing...uses IRQ4 <-- WHATPORT incorrectly reports IRQ3.

I keep my mouse on COM2 and it does not interfere with any of the other
serial ports as it has it's own, non-shared IRQ. My COM3 and COM4 ports
can be jumpered to either IRQ3 or IRQ4.

The author of this program is unknown. There is no copyright listed in
the program and can be assumed to be Public Domain.