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read only memory: a storage device that holds data permanently and cannot in normal circumstances be altered by the programmer
A unit of electrical conductivity, equal to the conductivity of a material in which an electric field of 1 volt per meter gives rise to a current density of 1 ampere per square meter. Derived from reciprocal ohm meter.
ROM(1) In an Android phone, a file for firmware updating. See Android ROM.
(2) (Read Only Memory) A memory chip that permanently stores instructions and data. Also known as "mask ROM," its content is created in the last masking stage of the chip manufacturing process, and it cannot be changed. Stand-alone ROM chips and ROM banks in microcontroller chips are used to hold control routines for myriad applications. ROMs were also widely used to hold the BIOS in early PCs as well as plug-in cartridges for video games.
Although EPROMs, EEPROMs, and particularly flash memory, are the kinds of non-volatile storage one hears about more often, ROM is a mature, inexpensive technology that is easy to integrate into the design of any CMOS chip.
ROMs Are Secure
Unlike flash memory, which can be updated, the data in ROM chips cannot be tampered with. If encryption keys and other security codes are stored in a ROM, they cannot be altered unless the chip is physically replaced (see secure boot). See memory types, RAM, EEPROM and flash memory.
|ROMs Are Everywhere|
|Cartridges that contain nothing more than a ROM chip are used to hold games and educational programs. The yellow ROM cartridge in this image (bottom right) contains a program for the LeapPad Learning System for preschoolers.|