Davex/doc/help/Dev

dev -- list, add, or remove ProDOS devices

syntax:  dev [-r<devnum>] [-a<devnum>] [-z]

ex:      dev
         dev -z
         dev -r.62
         dev -a.32

With no options, prints list of device numbers ProDOS scans 
when looking for an unknown volume.  With -r, removes the
specified device from the list.  With -a, adds the specified
device to the list.

-z (zap) scans all devices in the device list and REMOVES 
the ones that don't have ProDOS volumes mounted.  This is 
especially useful if you have Disk IIs that you will not use 
for a while.  (The next time you re-enter ProDOS 8, all your
disk devices will again be present in ProDOS's scan list.)

Note:  with -a, the low nybble of the device number is 
always set to 0.  This is not usually a problem.