What are RAM and ROM ? How are they alike ? How are they different ? What are EEPROM, PROM and EPROM?

RAM refers to Random Access Memory where both read and write operations can take place. But the RAM is a volatile memory and its contents are lost when power is turned off.

ROM refers to Read Only Memory where only read operation can take place. It does not have a write capability. ROM is a non-volatile memory.

RAM and ROM are the main memory of a computer and both of them are required for the smooth functioning of a computer system.

The RAM provides memory for reading as well writing and its contents can be modified as and when required. ROM, on the other hand, stores some instructions which are permanent. ROM cannot be written onto. One can only read instructions from ROM.

EEPROM refers to electrically erasable programmable ROM. In EEPROM, the EPROM is erased electrically which is faster. Also, with EEPROM, selective bytes can be erased unlike UV-EPROM which erases fully.

PROM refers to programmable ROM. It is a user-programmable memory in which information is burnt using special equipment called a ROM burner. It can be programmed only once.

EPROM refers to erasable programmable ROM. In EPROM, one can program the memory chip through various mechanisms (e.g., UV radiation) and erase it as many times as needed. The UV-EPROM can take up to 20 minutes for erasing EPROM contents.