Why Classic ROMs were not possible to Flash ?

We know that latest ROMs i.e Flash ROMs can be flashed as many times you want (limited to few million times I guess). But, the first ROM was not possible to flash once data was inserted in it.
What was the technical reason behind that ?

Okay, I know EPROM & EEPROM can be flashed, but I am talking here about firstROM, simple classic ROM in which once data was inserted it was not possible to insert data again.
What's the technical/scientific reason ?


  • Jeffrey Arulraj
    Jeffrey Arulraj
    In predetermined ROM AND PROM the method used to construct a bit in those devices are irreversible and can't be reset by sending any pulses of energy

    The reconstruction of transistor after the data is once written was not feasible those days

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