Read Only Memory (ROM)

ROM means Read Only Memory, it is a class of storage medium used in computers and other electronic devices. In RAM stored data cannot be modified, or can be modified in slowly or with difficulty, so it is mainly used to distribute firmware.ROM retains its contents even when the computer is turned off. ROM is referred to as being nonvolatile, whereas RAM is volatile.
Most personal computers contain a small amount of ROM that stores critical programs such as the program that boots the computer. In addition, ROMs are used extensively in calculators and peripheral devices such as laser printers, whose fonts are often stored in ROMs.

Other types of non-volatile memory such as erasable programmable read only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM or Flash ROM) are sometimes referred to, in an abbreviated way, as "read-only memory" (ROM), but this is actually a misnomer because these types of memory can be erased and re-programmed multiple times