ROM (Read Only Memory)
- A memory storage device, whose contents can be read and accessed but cannot be modified, so the name Read Only Memory.
- 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.
ROM's in development phase
- RRAM (Resistive Random access memory)
- Racetrack memory
- NRAM (Nano RAM)