Memory group called Read Only Memory also has characteristics that match the name. Existing data in ROM, this is data that has been entered by the manufacturer. The data already contained in it can not be changed again through the normal process, and can only be read only. There are pieces of data in ROM is used for the identity of the computer itself. It is stored in the BIOS (Basic Input Output System). There are also data contained in this module was first accessed by a computer when it boots. Sequences contained in this module and are accessed the first time when the computer is turned on is called bootstrapping.
In this bootstrap process, carried out some instructions such as checking the internal components supporting the work of at least one computer system, such as checking ALU, CU, BUS supporter of the motherboard and processor, check the main BIOS, check the graphics card BIOS, check the Memory Module, check for the presence Secondary Storage which can be a floppy disk, hard disk, or CD-ROM drive, then just check the MBR (Master Boot Record) of the storage media designated by the BIOS (in the Boot Sequence). The following will be discussed types of ROM and its development.
PROM (Programmable ROM)
ROM provides an opportunity for users to modify data stored by default. A device called PROM programmer in charge of "burn" (burn in) this chip. With a strong electric current bit location will burn and showed a value (0 or 1). After going through the process burningin, this PROM can no longer be changed contents.
EPROM (Erasable Programmable ROM)
This chip is the development of PROM. Only, this EPROM can be erased its previous contents using ultraviolet light. These rays pass through a gap in the collection of chips. Thus, the charge stored can be released. In other words, EPROM can be erased with ultraviolet light and reprogrammed electrically.
EEPROM (Electrically Erasable Programmable ROM)
This chip is not much different from the EPROM, EEPROM data but can be removed without the use of ultraviolet light. Just use electrical pulses (electrical pulses). Types of ROM such as PROM, EPROM and
EEPROM memory is classified into stable (nonvolatile memories). That is, these three types of ROM memory will keep its data even when not fed by electrical current. In development, the EEPROM chip has been used for the BIOS of a motherboard. By using the technique of "flash", the contents of the BIOS can be made later (update). However, the danger of flashable BIOS is all people can change the contents, including viruses. If you have been changed by a virus, then used a computer motherboard that will not be used again.