A USB drive consists of two fundamental elements, beside the mandatory USB connection and the optional status LED:
I) A manufacturer-specific controller chip with two essential functions. This constitutes first of all the USB interface with the Universal Serial Bus (from there the name USB). The USB interface at the PC constitutes the USB master. Second, the chip is responsible for the control of one or several Flash EEPROM and ensures that data are correctly written, read and deleted.
II) A Flash EEPROM ("Flash Electrically Erasable Progammable Read Only Memory") as a fast, electrical, erasable and programmable read-only memory. It is a read-only memory, i.e., memory contents remain even without power.