ROM is an acronym for Read-Only Memory. It refers to computer memory chips containing permanent or semi-permanent data. Unlike RAM, ROM is non-volatile; even after you turn off your computer, the contents of ROM will remain. There are different types of ROM, they are:
ROM means read-only memory.
It can only read.
It is a non-volatile memory.
When the computer switch is off, then its contents will not be lost or deleted.
So, it is a permanent memory.
ROM can be divided into three parts.
PROM(Programmable read-only memory)
EPROM(Erasable PROM)
EEPROM(Electrically Erasable PROM)
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Figure: ROM
Programmable ROM(PROM).
It is also called one time programmable ROM and can be written to or programmed using a special device called a PROM programmer.
Its contents cannot be erased or lost.
The working of a PROM is similar to that of a CD-ROM.
E.g. Firmware, CD-R
Erasable PROM(EPROM)
Information stored can be lost in ultraviolet light and reprogrammed whenever necessary.
E.g. CD-RW
Electrically Erasable PROM(EEPROM).
Its contents can be lost by electricity & again it can be programmed like EPROM.
E.g. Flash memory(Pen drive), memory card, etc.
Flash ROM:
Also called Flash BIOS or flash memory. This memory should be constantly powered and act as non-volatile memory in the computer.
The function of Flash ROM are
▪ Power On Self Test(POST) – Checks the major hardware components
▪ BIOS Setup program – built-in utility in BIOS which control how the computer works i.e. system settings, find bootable devices, interrupt handlers and device drivers
▪ Bootstrap loader: is a program to start the computer software for operation when the power is ON.
