Memory ROM (Read Only memory) is a type of memory where the data and instructions are stored by the manufacturer at the time of manufacture.
The ROM memory is a memory type that can store the data permanently or semi.
The data or instructions stored in ROM memory can only be read, and it is almost impossible or difficult to write new data. This is the reason why it is called read-only memory.
The ROM memory stores data and instructions permanently, and when the electrical power is switched off, the data stored in the ROM is not lost. This is the reason why the ROM is called nonvolatile memory.
The ROM memory is used more frequently to store boot instructions from the PC, that is, the BIOS – Basic Input Output System (that program that goes into action as soon as we turn on the computer).
ROM Memory Types
The three main types of ROM memory that have been used on computers are as follows:
- PROM-Programmable ROM
- EPROM-Erasable Programmable ROM
- EEPROM-Flash ROM
No matter what type of ROM memory your system uses, the data stored in a ROM is not volatile and remains indefinitely unless you use special methods (in cases where it is possible).
As the name implies, these are memories that can be programmed through special devices. The PROM is a type of ROM memory that is produced without any stored information. The user then, possession of appropriate equipment is able to perform only one recording of values in their cells.
This type of memory only allows it to be a single program once, getting hopelessly lost if we want to change the inserted pogram.
EPROM-Erasable Programmable ROM
A very popular variation of the prom is the EPROM. An EPROM has as its main feature the ability to allow the contents of its cells to be altered when illuminated with light violet
EEPROM-Eletronic eprom/flash ROM
A more advanced type of ROM is the EEPROM, which means PROM erasable electrically. These chips are also called flash ROM and are characterized by their ability to be reprogrammed directly on the circuit board without any special equipment.
When using an EEPROM, or Flash ROM, you can erase and reprogram the ROM of the motherboard on a PC without removing the system chip or even open the computer case.
On the PC this type of ROM memory is where the BIOS, POST and SETUP programs are stored.