What is "eeprom"

EEPROM (also written EPROM and pronounced "e-e-prom", "double-e-prom" or "e-squared-prom") stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store relatively small amounts of data but allowing individual bytes to be erased and reprogrammed.

EEPROMs are organized as arrays of floating-gate transistors. EEPROMs can be programmed and erased in-circuit, by applying special programming signals. Originally, EEPROMs were limited to single byte operations which made them slower, but modern EEPROMs allow multi-byte page operations. It also has a limited life for erasing and reprogramming, now reaching a million operations in modern EEPROMs. In an EEPROM that is frequently reprogrammed while the computer is in use, the life of the EEPROM is an important design consideration.

Unlike most other kinds of non-volatile memory, an EEPROM typically allows bytes to be read, erased, and re-written individually. EPROMs are erased by exposing a chip to ultra-violet light to erase its entire contents. Flash EPROMs are electrically erased and programmed but only as groups of bytes, ranging from tens to tens of thousands of bytes for different devices.