What is ROM in a computer?

Answer 1

ROM should be thought of as storage which is written and then cannot be changed. Once written the only way to destroy the data is to destroy the device holding the data.

A good example of ROM (Read Only Memory) would be a CD or DVD disc. Once written, the data on the discs cannot be changed, with the exception of Rewritables which were designed specifically for that purpose but even those cannot be re-written on the fly; they need permanent 'tracks' written to them, each time the data is changed which can be thought of as defined beginnings and ends to the data on the disc. (Re-Writables use a dissolvable chemical so that data can be 'smoothened out' and re-written as needed, whereas non re-writables just use a chemical film. Tiny holes burned into the chemical or film as data is written, when the computer reads the disc, it reads a pattern of binary 1s and 0s as it reads the pattern of gaps on the disc).

Solid state drives such as a lot of the smaller mp3 players or usb thumb drives are an example of EEPROM (Electronically Erasable Programmable Memory). The data on EEPROM can be manipulated electronically. Also in this category are SD Cards, Memory stick duos and similar, as well as the BIOS chip on a motherboard and firmware chips stored on many electronic devices. They are called solid state drives collectively because they are used for similar purposes as hard drives but have no moving parts.

- Hard drives (also known as Hard Disks) are not an example of ROM as they are designed to store and delete files a lot of the time on the fly. Even files stored on the hard drive permanently can be erased at the users discretion so anything on a hard drive even if given read only status in its file properties cannot be defined as ROM.

Answer 2

Read-only memory (ROM) is computer memory on which data has been prerecorded by the manufacturer. The data cannot be removed and can only be read. The data is there to start and organise the booting-up of the computer.