# erasable programmable read-only memory

> nonvolatile memory chip comprising an array of floating-gate transistors individually programmed by an electronic device that can be erased by other means, e.g. UV irradiation

**Wikidata**: [Q378210](https://www.wikidata.org/wiki/Q378210)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/EPROM)  
**Source**: https://4ort.xyz/entity/erasable-programmable-read-only-memory

## Summary
Erasable Programmable Read-Only Memory (EPROM) is a nonvolatile memory chip formed on an integrated circuit. It consists of an array of floating-gate transistors that are individually programmed by an electronic device. Unlike standard ROM, an EPROM can be erased, typically through exposure to strong ultraviolet (UV) light, and reprogrammed.

## Key Facts
- **Classification**: EPROM is a type of integrated circuit and nonvolatile memory.
- **Composition**: The chip comprises an array of floating-gate transistors used to store data.
- **Programming**: Data is written individually to the transistors by an electronic device.
- **Erasure Method**: The memory is erased by exposure to strong ultraviolet (UV) light.
- **Distinct from EEPROM**: EPROM is explicitly different from Electrically Erasable Programmable Read-Only Memory (EEPROM), which allows individual bytes to be erased and reprogrammed in-circuit via electrical signals.
- **Aliases**: Also known as E-PROM, Erasable Programmable ROM, and Rprom.
- **Variants**: UV-EPROM is a specific class of this memory type.
- **Historical Hardware**: The Soviet Union produced a series of these integrated circuits known as the 573 series.

## FAQs
### Q: How is an EPROM erased?
A: An EPROM is erased by exposing it to strong ultraviolet (UV) light. This process clears the data stored on the floating-gate transistors, allowing the chip to be reprogrammed.

### Q: What is the primary difference between EPROM and EEPROM?
A: While both are nonvolatile memory types, EPROMs are erased via ultraviolet light, whereas EEPROMs are erased and reprogrammed electrically within the circuit.

### Q: What physical component stores the data in an EPROM?
A: Data is stored in an array of floating-gate transistors. These transistors retain the electronic charge even when power is removed, classifying the device as nonvolatile.

## Why It Matters
Erasable Programmable Read-Only Memory represents a critical development in the history of computing and electronics. Before the widespread adoption of Flash memory, EPROMs provided a vital solution for developers who needed to update firmware or microcode without physically replacing hardware components. The ability to erase and rewrite nonvolatile memory allowed for the debugging and evolution of software in embedded systems, early computers, and microcontrollers.

The technology bridges the gap between one-time-programmable chips and modern electrically erasable storage. By utilizing floating-gate transistors—a technology still fundamental to modern Flash memory—EPROMs demonstrated that data could be retained without power yet remain mutable under specific conditions. The distinctive design requirement of a quartz window (to allow UV light in) made these chips easily recognizable and served as a physical manifestation of the transition from permanent hardware to updatable firmware. The distinction between EPROM and EEPROM (Electrically Erasable PROM) further highlights the industry's shift toward greater convenience and in-circuit reprogrammability.

## Notable For
- **Reprogrammability**: Unlike standard Read-Only Memory (ROM), it allows for the erasure and rewriting of data.
- **UV Erasure**: It is distinguished by its requirement for strong ultraviolet light to clear memory contents.
- **Floating-Gate Technology**: It utilizes an array of floating-gate transistors to achieve nonvolatile storage.
- **Hardware Distinction**: It differs from EEPROM, which uses electrical signals for erasure rather than UV light.

## Body
### Structure and Technology
An Erasable Programmable Read-Only Memory (EPROM) is an integrated circuit constructed as an array of floating-gate transistors. As a nonvolatile memory chip, it retains stored data even when power is removed from the device. The chip is classified as a type of read-only memory and is closely related to other memory technologies, serving as a distinct precursor to electrically erasable variants.

### Programming and Operation
The programming of an EPROM is performed by an electronic device that individually configures the floating-gate transistors. Once programmed, the data remains stable. The defining characteristic of an EPROM is its method of erasure. To clear the memory and prepare it for new data, the chip must be exposed to a strong source of ultraviolet (UV) light.

### Comparison with EEPROM
Although EPROM is categorized under the broad umbrella of nonvolatile memory arrays, it is structurally and functionally different from EEPROM. While EEPROM allows individual bytes to be erased and reprogrammed in-circuit using special programming signals, standard EPROMs require removal from the device (unless specifically designed with a UV source on board) and a bulk erasure process via UV light. This distinction highlights the technological evolution from light-erasable to electrically-erasable memory.

### Historical Context and Variants
Specific variants of this technology include the UV-EPROM. Historically, these chips were produced in various series, such as the 573 series integrated circuits manufactured in the Soviet Union. The technology is widely recognized under various names and abbreviations, including E-PROM and Rprom, and has been documented in major encyclopedic sources including Treccani and Encyclopædia Britannica.

## References

1. [OpenAlex](https://docs.openalex.org/download-snapshot/snapshot-data-format)