ROM

ROM is known as the Read-Only memory.It is a semiconductor-based memory that contains instructions or data that can be read but not modified.Generally, the term ROM often means any read-only device, as in CD-ROM for Compact Disk, Read Only Memory. Once data has been written onto a ROM chip, it cannot be removed and can only be read. Unlike main Memory (RAM), ROM retains its contents even when the computer is turned off and ROM is referred to as being nonvolatile. ROM stores the instruction that is used by the CPU. It tells the CPU how to be the kind of computer it is, for example a Windows, Macintosh, or Play Station computers.ROM also tells the CPU how to work with the different parts of the computer.ROM can also hold programs that are directly accessed by the CPU. One such program is the self-test when the computer is first turned on. The self-test tests to seem if all the parts on the main circuit board (mother board) are working correctly.These instructions in ROM are called firmware.In order to change the instructions in ROM you need to usually change the chips or do some other special process that is normally not available to an average user.In addition, ROMs are used extensively in calculators and peripheral devices such as laser printers, whose fonts are often stored in ROMs.There are a variation of ROM that is the Programmable read-only memory(PROM),Erasable programmable read-only memory (EPROM) and · Electrically erasable programmable read-only memory (EEPROM).