EPROM silicon chip. Scanning electron micrograph (SEM) of the etched surface of part of an EPROM silicon chip. Here, narrow tracks form part of the chip's circuitry; at left are rows of memory cells. This is an integrated circuit. The chip is of the EPROM type: Electrically Programmable Read-Only Memory. EPROM chips are programmed by applying a voltage across selected connecting pins. The memory cells can be switched electrically so that the chip stores the information programmed into it. By shining ultra- violet light on the chip, the programming is erased and it can then be reprogrammed. Magnification: x180 at 6x4.5cm size.