Read only memory
EEPROM -Electronically erasable programmable read only memory
Read only memory is another type of primary memory. It has no moving parts and it is electronic. There are several different types of ROM and they represent different stages in the development of this type of memory. As with so many computer names is misleading because several different types of ROM are not read only... they can be written to.
The most important difference between RAM and ROM is that ROM is non volatile, which means that all ROM chips keep their data after the power is turned off. This is essential when you need boot a computer up..... it is a bit of a conundrum! it is impossible to boot a computer without on operating system in place to copy the data from the hard drive to the RAM. That operating system is a low level operating system that is stored on a ROM chip on the motherboard and when the power is turned on the BIOS (basic input output system, a simple operating system with no user interface) is run from the ROM chip that it is stored on. If we had to rely on RAM to store the BIOS we would never be able to boot the computer because the RAM chip would be empty.
ROM chips are found all over the motherboard and controller cards. They store the firmware that is in control of the functioning of that card. Most modern ROM chips are made a of a type of electronically erasable programmable read only memory that can have the data stored on it erased and rewritten., This process is known as flashing.
IT is important to note that the erasing and rewriting of the data on a ROM chip cannot be done while it is in use. This is why you need a special piece of software that can communicate with the chip while it is disabled.
ROM chips are in use in a wide range of electronic devices from microwave ovens to remote control cars to washing machines, your calculator and even your watch.
There is often confusion surrounding the CMOS and the CMOS battery and the BIOS.... let us try to clear this up.
The CMOS is a type or volatile memory(loses data when not powered). it is installed on the motherboard