read only memory is a type of non-volatile memory used in computers, mobile and other electronic devices. It is very difficult to modify the available data in a normal way, or not because it is mainly used by Firmware (this is a type of software which runs hardware attached to the device) or application software in plug-in Used to store. ROM relates to an as memory that is hard-wired. Can not be changed after construction. But only a few circuits can be changed on the principle. Like if the data is bad or requires an update
TYPE OF ROM
Programmable read only memory or a time programmable ROM is written on a special side device, called prom programmer. Generally, this device is permanently destroyed or internal voltage of the internal link (fuses or antifascist) inside the chip uses it. A PROM can be programmed only once.
Erasable programmable read-only memory can be exposed to strong ultraviolet light (usually for 10 minutes or more). Then it can be written again with that process. Which again requires more voltage than the normal voltage. Repeated exposure of ultraviolet light will eventually become an EPROM wire, but the stamina of removing and re-programming of most EPROM chips is more than 1000 cycles. The EPROM chip package can often be identified by the leading quartz “window”, which allows ultraviolet light to enter. After programming, the window is usually covered with a label to prevent accidental erosion.
Electrically erasable programmable read-only memory is based on the semiconductor structure towards an EPROM. All of its contents can be electrically deleted and then electrically written. So it does not need to be removed from the device. An EEPROM can burn and burn very slow milliseconds per bit.
Electrically alterable read-only memory (EAROM) is a type of EEPROM that can be modified a bit at a time. The writing process of EAROM is very slow process and high voltage 12v is used to read it. EAROMs are desirous of those applications. For those who need occasional and partial rewriting, it is used as a non-volatile stroge for critical system setup information. In many applications, EAROM is supplied with back up with CMOS RAM and lithium battery supplied by the main power.
FLASH MEMORY :-
This is a modern type of EEPROM, which was invented in 1984. Comparison of a common EEPROM, the flash memory can be quickly written and erased. And new features have a lot of tolerance.