What is a ROM Memory ?
ROM is the read-only memory.It is different from RAM.It is the solid-state semiconductor memory only read the beforehand stored data . Its characteristics is that as soon as the data storaged it can not be changed or deleted. ROM of the stored data is stable, the stored data will not change in the power off.Its structure is relatively simple, the read-out is more convenient, and thus commonly used for storing various fixed program and data,such as the computer BIOS chip.Becasue ROM can not rewrite the information and can not be upgraded, it is now rarely used.
For ease of use and high-volume production, the further developments of ROM are Programmable ROM (PROM),Erasable Programmable Read Only Memory (EPROM),Electrically Erasable Programmable Read Only Memory (EEPROM),Flash ROM.etc..
Flash ROM is the useful .Flash ROM write fast,can write with low voltage. It has large capacity and low cost.It is used in Compact Flash/CF，Smart Media/SM，Security Digital/SD，Multimedia Card/MMC，Memory Stick/MS, and also used in PDA ,Pocket computer ,andriod smartphone.
This address is http://www.computerites.com/computer-basics/2012/12/what-is-a-rom-memory-615.html