 EEPROM |
 UV EPROM ERASER |
The term EPROM is an acronym that stands for 'Eraseable Programmable Read Only Memory'. EPROMS were the first reprogrammable Read Only Memory (ROM) used in modern computers. ROMs have their contents 'burned in' and this content cannot be changed, even if there are errors. This makes fixes and updates harder with ROM because the contents cannot be changed once it has been 'burned'.
Like ROM, EPROMs are able to hold their value even when the electrical power is off. An EPROM can be erased by exposing it to ultraviolet light and then 'reprogrammed' with new instruction code and data. This makes an EPROM more flexible and much more useful, especially if the device that uses it needs to become smarter over time. However, unlike ROM, the contents of an EPROM can be changed by exposing the chip to higher than ultraviolet light. The EPROM is first programmed at the manufacturing plant by exposing the chip to ultraviolet light of a certain intensity that erases the chip. New program code can then be loaded into the chip, the voltage stepped up to 'burn' the values into the chip and then the chip is ready for use.
EPROMs are used not only in computers, but in many of today's modern electronics. Examples of EPROMs you can hold in your hand include compact flash, smart memory, memory sticks etc. Computer BIOS is frequently stored in EPROMs.
See also:
The evolution of computer ROMs.