Radio Shack TRS-80 Model II Reference Manual page 262

-Modell! TRSDOS
The example programs supplied on the original system disk that use high-RAM
subroutines (DATMXX, EXDATMxx, COMSUBXX, BASCOMxx, etc.) and the DO files
to setup these (DOCOMXX) all demonstrate the correct way to use high-RAM
subroutines below the lowest of the system's high-RAM modules. Examine these
for the techniques, and addresses used. For full operational flexibility, it is
recommended to stay away from the high-RAM areas.
It is also possible that in future releases of the TRSDOS operating system, more
features or routines will be available that will use this space in high-RAM. You
should keep this in mind whenever you design your applications; the next features
might be exactly what you need (or desire) and that, in order to use these features,
you will have to modify your high-RAM subroutines. Consider the efforts required
to make these program changes, especially if your application program(s) are not
easy to modify, or it is not easy to get revised copies out to the users.
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