What is ROM
What is Computer ROM
ROM stands for Read Only Memory. The memory from which we can only read but cannot write on it. This type of memory is non-volatile. The information is stored permanently in such memories during manufacture. A ROM stores such instructions that are required to start a computer.
ROM is a storage medium that is used with computers and other electronic devices. As the name indicates, data stored in ROM may only be read. It is either modified with extreme difficulty or not at all. ROM is mostly used for firmware updates. A simple example of ROM is the cartridge used with video game consoles, which allows one system to run multiple games.
Types of ROM
There are different types of ROM;
- MROM (Masked ROM)
- PROM (Programmable Read Only Memory)
- EPROM (Erasable and Programmable Read Only Memory)
- EEPROM (Electrically Erasable and Programmable Read Only Memory)
Mask ROM: This is the type of ROM for which the data is written during the manufacturing of the memory chip.
PROM (Programmable Read-only Memory): The data is written after the memory chip has been created. It is non-volatile.
EPROM (Erasable Programmable Read-only Memory): The data on this non-volatile memory chip can be erased by exposing it to high-intensity UV light rays.
EEPROM (Electrically Erasable Programmable Read-only Memory): The data on this non-volatile memory chip can be electrically erased using electron field emission
Features of ROM
Permanence: The values stored in ROM are always there, whether the power is on or not. A ROM can be removed from the PC, stored for an indefinite period of time, and then replaced, and the data it contains will still be there. For this reason, it is called non-volatile storage. A hard disk is also non-volatile, for the same reason, but regular RAM is not.
Security: The fact that ROM cannot easily be modified provides a measure of security against accidental (or malicious) changes to its contents. You are not going to find viruses infecting true ROMs, for example; it's just not possible. (It's technically possible with erasable EPROMs, though in practice never seen.)