The following information has been excerpted from Beneath Apple ProDOS
by Gary B. Little, Addison-Wesley Publishing, ISBN 0-201-15008-5.

According to Gary's book, the PRODOS system file uses the following
memory locations:

  o $BF00-$BFFF in main RAM
  o $D000-$DFFF in $Dx bank1 of main bank-switched RAM
  o $D100-$D3FF in $Dx bank2 of main bank-switched RAM
  o $E000-$FFFF in main bank switched RAM

In addition, the following memory locations are reserved by ProDOS:

 o $03ED-$03FF in main RAM
 o $D000-$D0FF in $Dx bank2 of main bank-switched RAM
 o $D400-$DFFF in $Dx bank2 of main bank-switched RAM

The ProDOS /RAM driver uses the following memory locations:

 o $003C-$0043 in auxilliary zero page
 o $0200-$03FF in auxilliary RAM
 o $0C00-$BFFF in auxilliary RAM
 o $D000-$FDFF in $Dx bank1 of auxilliary bank-switched RAM
 o $D000-$DFFF in $Dx bank2 of auxilliary bank-switched RAM

The following locations are not used by /RAM, but are marked as used
in its bitmap.

 o $0400-$07FF for video RAM (in 80-column mode)
 o $0800-$087F for serial buffer (existing in Apple IIc only)
 o $0880-$08FF for keyboard buffer (existing in Apple IIc only)
 o $0900-$0BFF is unused, but supposedly reserved
 o $FFFA-$FFFF for mirroring main bank-switched RAM vectors

With the /RAM driver installed, the only free locations to work with
are the following:

 o $0000-$003B in auxilliary zero page
 o $0044-$00FF in auxilliary zero page
 o $0900-$0BFF in auxilliary RAM
 o $FE00-$FFF9 in auxilliary bank-switched RAM

Here is a quote that immediately follows the memory locations I just
listed:

    "Despite the apparent availability of these areas, they should be
     considered reserved for future use by later versions of ProDOS 8
     and must not be used by nonsystem software."

