Erasible Programmable Read-Only Memory or EPROM, is a computer memory chip that retains data even after a power failure - that is, non-volatile (non-volatile). It is a set of floating-gate transistors that are programmed separately by an electronic device that provides higher voltage than is commonly used in electronic circuits. Once the program is complete, the EPROM can only be erased by intense ultraviolet radiation. EPROM is easily identified by a transparent window with silicon visible at the top of the package, which is also used for UV erasing.

Erasible Programmable Read-Only Memory (EPROM) is a RAM memory that can be erased and reprogrammed. It must be erased by illuminating the transparent window on its IC card with ultraviolet light before writing. This type of chip is easier to recognize and contains a "quartz glass window" in its package. A programmed EPROM chip's "quartz glass window" is usually covered with black sticker paper to prevent direct sunlight.

The contents of the EPROM can be erased and rewritten by special means. The basic unit circuit (storage cell) of the device usually uses floating gate avalanche injection MOS circuit, referred to as FAMOS for short. Similar to MOS circuits, two P-type regions with high concentration are grown on N-type substrates, and the source S and drain D are separately induced by ohmic contact.

There is a polycrystalline silicon grid floating in the SiO2 insulation layer between the source and the drain, with no direct electrical connection around it. This circuit represents memory 1 or 0 by whether the floating grid is charged or not. When the floating grid is charged (for example, a negative charge), just below it, a positive conduction channel is induced between the source and the drain, which makes the MOS tube conductive, that is, memory 0. If the floating grid is not charged, no conductive channel is formed and the MOS tube is not conductive, i.e. stored in 1.