Read Only Memory

ROM

ROM is read only Non-Volatile memory written data into it while manufacturing. Data of Rom never get change in its entire life.

Example : BIOS,Firware,Console

PROM

PROM is Non-Volatime memory manufactured blank, a user writes program into it. Ones data written in PROM it never get change. PROM is permanent it retain its data when power goes off. you need a special device called a PROM programmer or PROM burner for writing data. The process of programming a PROM is sometimes called burning the PROM.

Example : mobile phones, Radio Frequency Identification cards (RFIDs), High Definition Media Interfaces (HDMI), and video game controllers

EPROM

EPROM is Non-Volatime memory  also manufacture blank, A user writes program into it. EPROM can reprogram many time when it’s required but PROM can program only one. UV light is used to write data. Today, EPROM chips are not used in computers and have been replaced by EEPROM chips.

Example : EPROMs you can hold in your hand include compact flash, smart memory, memory sticks etc. Computer BIOS is frequently stored in EPROMs.

EPROM Writer

Difference between PROM and EPROM

PROM	EPROM
PROM is the older technology	While both PROM and EPROM is nonvolatile memory devices. But EPROM in trend.
PROMs data is written/ programmed onto the chip by blowing the fuses at each bit using much higher voltages than the average voltages used in digital circuits	EPROMS also use high voltage, but not enough to alter the semiconductor layer permanently.
The process in the programming of PROMS is irreversible; hence the memory is permanent	In EPROMs memory can be erased by exposure to UV light.
you need a special device called a PROM programmer or PROM burner. The process of programming a PROM is sometimes called burning the PROM.	Data can be erased by exposing it to ultraviolet light. Once it is erased, it can be reprogrammed. An EEPROM is similar to a PROM, but requires only electricity to be erased.
This is similar to ROM except that you, the consumer, can program it.  You can buy a blank chip and have a PROM programmer program it with your stuff.  But, once you program it, you can never change it.	So the cool this about this one is that you can rewrite this type of memory.  To erase a previous program though, you need to set it under some form of UV light for a specified amount of time before being able to rewrite it.
A company can used PROM when no change will have to apply in future.	A company may use EPROM over ROM anytime they need something different for each device, like a serial number.

 Writing Process Video of EPROM

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