What Is ROM?

Date First Published: 19th June 2023

Topic: Computer Systems

Subtopic: Computer Hardware

Article Type: Computer Terms & Definitions

Difficulty: Medium

Difficulty Level: 6/10

CONTENTS

Types Of RAM
Difference Between ROM and RAM

Learn about what ROM in this article.

Stands for Read Only Memory. ROM is a form of permanent and non-volatile memory that computers can read but not write to or remove. ROM is useful for storing software that is not expected to be changed during the lifetime of a system, like the firmware, which contains the programming needed to boot a computer and the necessary instructions it needs to operate and communicate with other hardware, like printers. Since the ROM is non-volatile, the data is not deleted after the power is removed.

ROM is not only used in computers, which use a special ROM chip that contains the BIOS firmware to carry out the basic tasks required to boot up and start the other components. ROM chips are found in all electronic devices that require software instructions to perform tasks, like calculators and laser printers, whose fonts are often stored in the ROM. In addition, it is used in optical storage, including different types of compact discs, like CD-ROM to distribute film and music. The cartridge in video game consoles uses ROM to allow the system to run multiple games.

Types Of ROM

Different types of ROM include:

Masked ROM - A type of ROM where the software instructions are programmed by the integrated circuit manufacturer instead of the user. It is masked off during production. This is the earliest form of ROM.
Programmable ROM - Also known as PROM, this type of ROM contains a memory chip where data can only be written once. Standard PROM can only be programmed once because PROM chips are manufactured with fuses. The chip is programmed by burning fuses, which is an irreversible process.
Ultraviolet-erasable ROM - A type of ROM whose contents can be erased using ultraviolet light and then reprogrammed with new data.
Erasable programmable ROM - A special type of PROM whose contents can be erased by exposing the circuits to an electrical charge at one byte at a time.
Electrically-erasable programmable ROM - Also known as EPROM, a type of ROM that can be erased electronically and reprogrammed multiple times. It is often used to store small amounts of data in computing and other electronic devices and enables simple firmware updates without requiring any other equipment.

Difference Between ROM and RAM

The terms 'ROM' and 'RAM' look similar, but they are two completely different types of memory. Read-Only Memory (ROM) is a form of memory that the computer can read but not write to, as suggested in the name. RAM can be read and written to. Another difference between ROM and RAM is that ROM is non-volatile, whilst RAM is volatile. This means that ROM keeps it data, even after the power is turned off, whilst the contents stored on the RAM are lost when the computer turns off.

ROM chips can only store a few megabytes of data, which usually ranges from 4 MB to 8 MB, whilst RAM chips can store several gigabytes of data. The storage of a RAM chip usually ranges from 1 GB to 256 GB.