ROM: Read-Only Memory
ROM (read-only memory) is nonvolatile memory, generally installed by the vendor of the computer during the process of manufacturing the motherboard or secondary components that need to retain code when the machine is turned off. With the use of ROM, information that is required to start and run the computer cannot be lost or changed.
ROM is used extensively to program operation of computers, as well as in devices like cameras, and controls for the fuel injectors in modern cars. However, ROM plays a limited role in the PC. Here, it holds the instructions for performing the POST routine and the BIOS information used to describe the system configuration. For more detailed information, refer to Tutorial 6, "Primary PC Components."
In most cases, a technician will need to be concerned with ROM only if it has failed and requires replacement, needs to be upgraded, or if it conflicts with other memory installed in the system. The actual code in ROM is not usually in the direct control of a repair person or technician.