What is ROM?
Most computing devices will not work without Read Only Memory (ROM). Everything from calculators to media players to computers, chips called ROM with built-in programs are used to accept user input, make display graphics, and access disks. ROM chips are useful because they are non-volatile, meaning that the information they contain does not depend on having power applied. ROM allows computers to start up even after they have lost power. Like most electronic components, ROM on a computer or other device can become damaged, usually resulting in the failure of the device.
In a computer, the basic input and output system (BIOS) is stored in ROM, allowing the computer to recognize hard disks, RAM, I/O ports and peripherals when it is turned on. Once the BIOS information is read, the computer can then begin to load the operating system so the computer is usable. This kind of program is called firmware and is found on motherboards, hard drives, graphics adapters, printers and more. In each case, the firmware configures the device and then communicates to the computer that the device is present and operational.
Originally, ROM chips were unchangeable once data were written to them. Now most devices have programmable ROM chips that can be erased and updated with new firmware using special update programs. This makes it possible for users to upgrade firmware to give devices new features rather than having to replace the entire device.
ROM is not limited to electronic chips. CD ROM, DVD ROM, and Blu-ray ROM contain enough non-volatile storage to contain computer application programs and a variety of user data. Like ROM chips, some types of ROM storage can be re-written under special circumstances.