ROM (Read Only Memory) commonly known as ROM is a computer memory type. It is manufactured with the use of fixed data device. This system also refers to computer memory chips that have pre-recorded, permanent, or semi-permanent programs.
As compared to RAM in which data is volatile, ROM doesn't have these issues. If you shut down the computer or you restart it, then also the memory will be available.
The data that is saved in ROM cannot be modified and this is why data can be stored in it permanently. ROM was invented in the year 1956 and since then there have been many modifications that have happened in it.
Masked ROM (MROM):
There are pre-programmed instructions and data that are there in masked ROMs. It is inexpensive.
Programmable read-only memory (PROM):
It is a read-only memory which can be modified only a single time by a user. A user can buy a blank ROM for the purpose of entering the desired contents with the use of PROM program. The memory in it is not erasable.
EPROM and EEPROM :
EPROM stands for erasable read-only memory and on the other hand, EEPROM stands for electrically erasable programmable read-only memory. EPROM can be erased when it gets exposed to the harsh ultraviolet rays for more than 10 minutes and it can also be rewritten by accessing high voltage. EEPROM is much more convenient as its content can be rewritten and erased electrically.
Advantages of ROM:
a) The data in ROM cannot be altered
b) Contents can be verified
c) It works as per the changes you make in your device
d) Performance is good
e) Improved battery life
f) Non-volatile memory
Disadvantages of ROM:
a) Memory cannot be altered
b) Number of write and reads are limited
c) Costly than hard disk