Programmable read-only memory (PROM), or one-time programmable ROM (OTP), can be written to or programmed via a special device called a PROM programmer
Erasable programmable read-only memory (EPROM) can be erased by exposure to strong ultraviolet light, then rewritten with a process that again needs higher than usual voltage applied
Electrically erasable programmable read-only memory (EEPROM) is based on a similar semiconductor structure to EPROM but allows its entire contents to be electrically erased, then rewritten electrically, so that they need not be removed from the computer