Programmable read-only memory

Programmable Read-Only Memory (PROM) is a type of read-only memory (ROM) that can be programmed directly by the user using a special PROM programmer. It is a control memory in which stored information can be altered, but not as easily as in ordinary memory.
A PROM that is able to be erased and rewritten is called an EPROM (standing for erasable programmable read-only memory). A PROM that is able to erased and rewritten only using electricity is called an EEPROM (standing for electrically erasable programmable read-only memory).