If all you mean to do is place read-only variables in program memory,
qualify them as const (see Objects in Program Space). If you intend the
variables to be located in the external program memory then use the
__far qualifier (see Far Type Qualifier) and specify the
memory using the -mram option (see Ram Option). The compiler will
allow __far-qualified variables to be modified. Note that the time to
access these variables will be longer than for variables in the internal data memory.
The access mode to external memory can be specified with an option (see Emi Option).