If your program needs additional RAM, the 9S08QG8 may not be suitable, and you will need to use a larger device. Flash memory is read-only, and cannot be directly written like RAM.
It is possible to use flash memory for non-volatile storage of data, but the flash must be programmed with the required data. This may be done from within the program code, but is much more complex than simply writing to a flash location. There is also a finite limit to the total number of times that a flash location may be erased, and then re-programmed.
I suggest that you use the search engine below (for the 8-bit forum) and you should find many examples that have been previously posted. You will also need to be familar with the flash programming requirements to be found within the datsheet for the 'QG8.
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