PROM or programmable ROM (programmable read-only memory) is a computer memory chip that can be programmed once after it is created. Once the PROM is programmed, the information written is permanent and cannot be erased or deleted. PROM was first developed by Wen Tsing Chow in 1956. An example of a PROM is a computer BIOS in early computers. Today, PROM in computers has been replaced by EEPROM.
EPROM is a non-volatile memory chip that was invented by Dov Frohman in 1971 while at Intel that can only be read. If exposed to ultraviolet light, an EPROM can be reprogrammed if needed, but otherwise does not accept or save any new data. Hardware manufactures use EPROM when it may be needed that the data contained on the EPROM needs to be changed. An EPROM chip is distinguishable by a small quartz crystal (not glass) circle window that exposes the chip so that can be reprogrammed. The picture on this page is an example of an Intel 8048 made by NEC and is an example of an EPROM chip.
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