Difference between ROM and PROM

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ROM : Read Only Memory
PROM : Programmable Read Only Memory

It had me confused for some time. But now I know for sure.

The similarity between ROM and PROM is that the program can be burned only once in both of them and it stays there forever. For the difference part, there are two major differences:
1. When the power is turned off to the system, PROM retains the data in it while it is erased in case of ROM
2. While to program is burned in ROM at the time of manufacture, in the case of PROM, nothing inside the memory at the time of manufacture. For burning program into it, a special hardware is required known as PROM programmer or PROM burner.

I couldn’t find a proper video programming the PROM, but here is something similar for EPROM.
PS: Hey, an interesting thing about EPROM is that it is erased using ultraviolet light. Fancy watching that live.