Generally, we know that ROM (Read-Only Memory) is a memory that cannot be changed. It is a non-volatile memory, meaning that these memory chips will not be affected when the power supply is turned off. There are many types of ROM. Two of these types are PROM and EPROM.

In this article, we will discuss the difference between PROM and EPROM but before distinguishing between PROM and EPROM, let us discuss the definition of PROM and EPROM.

What do you understand by PROM?

PROM is the acronym for Programmable Read Only Memory. It is one of the types of ROM, i.e., Read Only Memory. Chinese-American missile guidance scientist and digital computer pioneer Wen Tsing Chow invented the PROM chip in 1956.

PROM is an empty memory chip. These are left blank during the manufacture of these chips. In this, the user can write only once. It is a permanent memory, meaning that once written, data cannot be erased or changed even when the computer is turned off. The memory of the PROM chip is always intact, and it will not be affected by power off or on.

PROM chips store data that you do not want to change. When the user buys a PROM chip, the chip is initially empty because the manufacturer has made this chip blank. The user provides the data that he wants to be stored in the chip and, with the help of the PROM programmer device, writes the content into it.

It is an OTP (One Time Programmable) memory from which the user can write data on these chips only for the first and last time.

PROM chips are used in video game consoles, microcontrollers, mobile phones, and medical devices.

What do you understand by EPROM?

EPROM is the abbreviation for Erasable Programmable Read Only Memory. It is also one of the types of Read Only Memory (ROM). It is non-volatile in nature, which means that data is retained when the power supply is turned off. Dov Frohman, an electrical engineer, invented the EPROM chip in 1971. We can erase the non-volatile memory by exposing it to ultraviolet light, and it takes several minutes for the data to be erased. The EPROM memory is erased with the help of a device called an EPROM eraser, and then the new data is stored again to reuse the EPROM chip.

The data that the EPROM chip stores can be erased for a limited time because erasing the chip too many times can damage it. EPROM can be used repeatedly by erasing old data and storing new data.

EPROM chips are used in microcontrollers to store data.

Key Difference between PROM and EPROM

PROM	EPROM
The complete form of PROM is Programmable Read Only Memory.	The complete form of EPROM is Erasable Programmable Read Only Memory.
A plastic wrap around it completely protects the PROM.	The EPROM is secured by placing it in a rock crystal window box so that ultraviolet light can pass through it.
It is a permanent memory, which means that the memory remains protected and is not lost when the power supply is turned off.	It is a non-volatile memory, but the memory is erasable and reprogrammable.
It can be written only one time after its manufacturing.	It can be rewritten by erasing the old data.
It is inexpensive and cheaper than EPROM.	It is expensive in comparison to PROM.
It can handle a lot of storage.	It can handle less storage.
The scalability and flexibility are more than EPROM.	The scalability and flexibility are less than PROM.
It is constructed using bipolar transistors.	It is constructed using MOS transistors.
The chip becomes unusable if any error occurred while writing to the PROM.	The chip can be erased, rewritten, and reusable if any error is encountered while writing to the EPROM.
It is One Time Programmable (OTP).	It can be programmable multiple times.
It is not reusable.	It is reusable.
It is not feasible to change the data contained in the PROM chip.	It is feasible to change the data contained in the EPROM chip.

The above table demonstrates the difference between Programmable Read Only Memory (PROM) and Erasable Programmable Read Only Memory (EPROM). From this table, we conclude that PROMs are cheap, but their data cannot be changed, and EPROMs are expensive but old data can be erased, and new data can be stored.