Read-only memory facts for kids
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Read-only memory (or ROM) is a special kind of computer memory. Unlike RAM, ROM keeps its information even when the computer or device is turned off. You usually cannot change what is stored on a ROM chip once it's made.
ROM is used for very important programs. For example, it holds the BIOS (Basic Input/Output System). The BIOS tells your computer how to start up when you turn it on. ROM also stores firmware, which is like the built-in software for devices such as printers or game consoles. These programs usually don't need to be changed. ROM chips are a type of computer chip.
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Different Kinds of ROM
There are several types of ROM, each with a slightly different way of storing and changing information.
Masked ROM
This type of ROM is made at the factory. The information is "written" onto the chip during its manufacturing process. Once it's made, you cannot change the information on a Masked ROM at all. It's very cheap to make many copies of this kind of ROM.
PROM (Programmable Read-Only Memory)
PROM chips come blank from the factory. You can program them one time using a special device. Programming a PROM involves permanently breaking tiny connections inside the chip. After it's programmed, you cannot change it again. Newer types of ROM have mostly replaced PROMs.
EPROM (Erasable Programmable Read-Only Memory)
EPROM chips are special because you can erase them! To do this, you shine strong UV light through a small window on the chip. This light clears all the information. Once erased, you can program the EPROM again with new information.
EEPROM (Electrically Erasable Programmable Read-Only Memory)
EEPROM chips are even more flexible. You can erase them using an electrical signal, not UV light. This means you can erase and reprogram them without removing them from the computer. Today, a type of EEPROM called flash memory is very common. Flash memory is used in USB drives, smartphones, and solid-state drives (SSDs).
Images for kids
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Many game consoles use interchangeable ROM cartridges, allowing for one system to play multiple games. Shown here is the inside of a Pokémon Silver Game Boy cartridge. The ROM is the IC on the right labeled "MX23C1603-12A".
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Transformer matrix ROM (TROS), from the IBM System 360/20
See also
In Spanish: Memoria de solo lectura para niños
