Programmable read only memory (PROM)

A PROM is a memory chip on which data can be written only one time. Once a program has been written onto a PROM, it's permanent. Unlike RAM, PROM's retain their contents when the computer is turned off. Difference between a ROM and a PROM (read only memory) is that a PROM is manufactured as a blank memory while a ROM is programmed during manufacturing process. To write data onto a PROM chip, a special device known as a PROM programmer or PROM burner is required.