Stands for "Programmable Read-Only Memory," and is pronounced "p-rom," not "prom" like the high school dance. PROM is a type of ROM that is programmed after the memory is constructed. PROM chips have several different applications, including cell phones, video game consoles, RFID tags, medical devices, and other electronics. They provide a simple means of programming electronic devices.
Standard PROM can only be programmed once. This is because PROM chips are manufactured with a series of fuses. The chip is programmed by burning fuses, which is an irreversible process. The open fuses are read as ones, while the burned fuses are read as zeros. By burning specific fuses, a binary pattern of ones and zeros is imprinted on the chip. This pattern represents the program applied to the ROM.
While PROM cannot be erased, two other versions of PROM have been developed that can be erased and reprogrammed. One type is called EPROM, or Erasable Programmable Read-Only Memory. This type of memory uses floating-gate transistors and can be erased by strong ultraviolet light. The other type is EEPROM, or Electrically Erasable Programmable Read-Only Memory. EEPROM can be erased with an electrical charge and is used in flash memory.