locations are:

     128,129   80,81    LOMEM
     130,131   82,83    VNTP
     132,133   84,85    VNTD
     134,135   86,87    VVTP
     136,137   88,89    STMTAB
     138,139   8A,8B    STMCUR
     140,141   8C,8D    STARP

     The string/array space is not loaded; STARP is included only to
     point to the end of the BASIC program.
     The two other critical BASIC page zero pointers, which are not
     SAVEd with the program, are:

     142,143   8E,8F    RUNSTK
     144,145   90,91    MEMTOP

     For more information concerning Atari BASIC, see the appendix.
     For detailed description, refer to the Atari BASIC Reference
     Manual. For more technical information, see De Re Atari, BYTE,
     February 1982, and COMPUTE!'s First Book of Atari and
     COMPUTE!'s Second Book of Atari.

---------------------------------------------------------------------------
Locations 49152 to 53247 ($C000 to $CFFF) are unused.
Unfortunately, this rather large 4K block of memory cannot be written
to by the user, so it is presently useless. Apparently, this area of ROM
is reserved for future expansion. Rumors abound about new Atari OS's
that allow 3-D graphics, 192K of on-board RAM and other delights.
Most likely this space will be consumed in the next OS upgrade.
PEEKing this area will show it not to be completely empty; it was
apparently used for system development in Atari's paleozoic age.
Although the Atari is technically a 64K machine (1K equals 1024 bytes,
so 64K equals 65536 bytes), you don't really have all 64K to use. The
OS takes up 10K; there is the 4K block here that's unused, plus a few
other unused areas in the ROM and, of course, there are the hardware
chips. BASIC (or any cartridge) uses another 8K. The bottom 1792
bytes are used by the OS, BASIC, and floating point package. Then
DOS and DUP take up their memory space, not to mention the 850
handler if booted -- leaving you with more or less 38K of RAM to use
for your BASIC programming.

---------------------------------------------------------------------------
Locations 53248 to 55295 ($D000 to $D7FF) are for ROM for the special
I/O chips that Atari uses. The CTIA (or GTIA, depending on which
you have) uses memory locations 53248 to 53503 ($D000 to $D0FF).
POKEY uses 53760 to 54015 ($D200 to $D2FF). PIA uses 54016 to 54271