CP/M user number

[Jonathan Harston]

The CP/M filesystem has a user number for each entry, selected

with the CCP USER command and the relevent BDOS function.

Normally the user number is 0-15, but CP/M 3 allowed the byte

in the filesystem to hold 0-31, and various CCPs allowed USER

to specify 0-31.

But.... location 0004 holds the drive and user number, with b0-b3

holding the drive 0-15=A-P  and b4-b7 holding the user number...

but four bits can only hold 0-15. Also, the CCP is entered with

C=USER*16+DRIVE on startup, which can only hold drive 0-15.

So, what happens on systems that allow USER 0-31. What happens

with location 4? What happens with C on entry to the CCP?

jgh