Q. Explain Read-only memory?

ROM is nonvolatile (because it maintains its contents even when its power is shut off) and is used to store data and programs that do not change during the operation of the system. The mask-programmed ROMs are read-only devices that are programmed for data storage during the manufacturing of the chip itself. These are generally less expensive devices for mass production. Character-font memory for laser printers is a good example. Programmable read-only memory (PROM) is a field-programmable memory that is fabricated by the manufacturer containing all 0s and is programmed irreversibly by the user by electrically changing appropriate 0s to 1s. PROMs are quite economical in small quantities. Erasable programmable read-only memory (EPROM) is nonvolatile and widely used in microprocessor systems for program storage. It can be erased by shining an ultraviolet light and reprogrammed if necessary. These are produced in lowtomoderate volumes.