ROM is a type of memory that stores the instructions, which are necessary for starting up the computer. It cannot be written like RAM because as the name implies they are read only memories. But, now few versions of ROM have been launched that include multiple enhanced features of reading and writing.
Various types of ROM are:
• Programmable Read Only Memory (PROM): Is a type of ROM chip, which allows you to write.
But, it provides permission to write on chip only once. The PROM cannot be updated further, if
it has been used.
• Erasable Programmable Read Only Memory (EPROM): Is a special type of PROM that provides update permission on a PROM memory chip. Unlike PROM, here you can erase the already programmed chip by exposing it to ultraviolet light.
• Electrically Erasable Programmable Read Only Memory (EEPROM): Is again a special type of PROM. It also allows you to erase the instruction and reprogram the chip like EPROM. But, here you can erase the chip by exposing it to an electrical charge.