Postoje 2 osnovne skupine memorije:
ROM i RAM
Zatim postoje pod skupine svake vrste!
Imaš ROM koji se može mjenjati no podaci gore ostaju nakon nestanka struje!
Evo i detaljnije:
Semiconductor based
Classic mask-programmed ROM chips are written to during production and cannot change content afterwards. But there are other types of non-volatile solid-state memory:
* PROMs (Programmable Read-Only Memory) can be written to (programmed) via a special device, a PROM programmer. The writing often takes the form of permanently destroying or creating internal links (fuses or antifuses) with the result that a PROM can only be programmed once.
* EPROMs (Erasable Programmable Read-Only Memory) can be erased by exposure to ultraviolet light then rewritten via an EPROM programmer. Repeated exposure to ultraviolet light will eventually destroy the EPROM but it generally takes many (greater than 1000) exposures before the EPROM becomes unusable. EPROMs can be easily identified by the circular 'window' in the top which allows the UV light to enter. Once programmed, this window is typically covered by a label to prevent accidental erasure.
* EAROMs (Electrically Alterable Read-Only Memory) can be modified a bit at a time, but writing is intended to be an infrequent operation; most of the time the memory is used as a ROM. EAROM may be used to store critical system setup information in a non-volatile way. For many applications, EAROM has been supplanted by CMOS RAM backed-up by a lithium battery.
* EEPROM such as Flash memory (Electrically Erasable Programmable Read-Only Memory) allow the entire ROM (or selected banks of the ROM) to be electrically erased (flashed back to zero) then written to without taking them out of the computer (camera, MP3 player, etc.). Flashing is much slower (milliseconds) than writing to RAM (nanoseconds) (or reading from any ROM).
* By applying write protection, read/write memory may be turned (temporarily) into read-only memory.
ostatak na:
http://en.wikipedia.org/wiki/Read-only_memory