Cassette BASIC did not include any built-in support
for disk drives.
'course it did have peek and poke, with which you could do "anything",
including talk to the FDC, or put machine language code into memory.
I'd love to see you talk to the disk controller with peek and poke :-).
It's not memory mapped. You need the port I/O commands which were
something like INP and OUT....
-tony