Read Only Memory (ROM)
It is not volatile, Stores crucial information essential to operate the system, like the program essential to boot the computer.
Types of ROM:
PROM
(Programmable read-only memory) – It can be programmed by user. Once programmed, the data and instructions in it cannot be changed.
EPROM
(Erasable Programmable read only memory) – It can be reprogrammed. To erase data from it, expose it to ultra violet light. To reprogram it, erase all the previous data.
EEPROM
(Electrically erasable programmable read only memory) – The data can be erased by applying electric field, no need of ultra violet light. We can erase only portions of the chip.
