Changes

After initialisation, the next two patches are helper functions, which occupy free space between CP/M modules. One is at 03E9h, in the gap between the CD and TE modules; the other at 0EE2h, in the gap at the end of DD. The first one backs up 128 bytes of memory at 8080h (which is normally used by the font) so it becomes available as a transfer buffer. The second reverses this, restoring the font.

The disk access functions follow; these are placed between 8960h and 89FFh, in memory that's probably reserved for the system message table. Since they page memory, they switch to a local stack, which grows down from 3CFEh.