What is the difference between PROM and EPROM?

EPROM (Electronic Programmable Read Only Memory) chips can be erased if it needs to be updated or fixed. It can be erased electronically only These are comparatively expensive than PROMs. PROM (Programmable Read Only Memory) chips are relatively once written and to rewrite them you need to replace entire data on it. These are relatively less costly.

PROM is the Programmable ROM that allows the user to store data. an instrument called a PROM programmer does the storing by 'burning in', once the data has been burned, the data cannot be erased!

On the other hand, an EPROM allows the data to be erased by the help of uv lights. i.e EPROM is uv light erasable and electrically reprogrammable.