How do you find out if a machine is 32 bit or 64 bit?

[Ian Collins]

Intstruciton sizes might be variable, but the whole instruction with
paratmers is usually fixed. Otherwise the IP will have unaligned
address which I doubt the CPU could fetch it and instruction acrossing
two words will make the CPU design insane...

ret?

 

[Kevin Handy]

Note that, as far as I remember, the first C implementation was on the
PDP-11, a 9-bits byte machine.

The PDP-11 is a 8-bit byte machine, 16 bit words, 16 bit pointers.

You may be thinking of the PDP-10, which was a 36 bit machine with
6, 8, or 9 bit bytes.