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Definition

• A memory storage device, whose contents can be read and accessed but cannot be modified, so the name Read Only Memory.

Description

• Also called as non-volatile memory.
• Holds the permanent programs to tell system how to use circuit board.
• Data is not lost even the computer is switched off or power failure.
• Data in this memory is read only.

Types of ROM

MROM (Mask-programmed ROM):

• It is programmed at the factory.
• Program or data is permanently installed at the time of manufacturing.

PROM (Programmable ROM):

• Can be custom-programmed by the user only once using special circuitry PROM programmer.
• This circuit uses high voltages to permanently eliminate or create inner links.

EPROM (Erasable-Programmable ROM):

• Can be programmed by the user using strong ultraviolet light and special circuitry.

EEPROM (Electrically Erasable PROM):

• Can be erased and reprogrammed by electrical signals.
• Manufacturing process is complex and expensive.
• Rarely used.