ROM or in its longest form read-only memory, is computer memory used in computers and other electronic devices.

As the name suggests, the data stored in the read-only memory storage medium is intended to be only red. This type of memory is used specially for firmware updates and application software in plug-in cartridges.

Modifications to data in the ROM are hard to do and usually they are not done at all.

There are different types of read-only memory storage medium solutions. These are divided into some main categories, including semiconductor- based and optical storage, such as a CD-ROM.

In the semiconductor space, there is the programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), and the electrically erasable programmable read-only memory (EEPROM).

Within EEPRON there are further types, including electrically alterable read-only memory (EAROM) and flash memory.

Historical ROM technologies include diode matrix ROM, resistors, core rope, and dimond ring stores.