jtw11:
I see, so if there were two external interrupts, only one queue event would be logged even though there are 2 requesting a log (if for example, they were)?
No. Each is a separate source.
Also, what is a pin change interrupt?
It's similar to CHANGE available for external interrupts (attachInterrupt( pin, CHANGE );).
Is that adding another interrupt pin using the PinChangeInt library?
Yes. But only for CHANGE. LOW, RISING, and FALLING are not available (but can be simulated and are simulated in one of the pin-change interrupt libraries).