Flash Memory and Flash Drive
Flash memory is an electronic ( solid-state ) non-volatile computer storage medium that can be electrically erased and reprogrammed. Toshiba developed flash memory from EEPROM (electrically erasable programmable read-only memory) in the early 1980s and introduced it to the market in 1984. The two main types of flash memory are named after the NAND and NOR logic gates . The individual flash memory cells exhibit internal characteristics similar to those of the corresponding gates. Where EPROMs had to be completely erased before being rewritten, NAND-type flash memory may be written and read in blocks (or pages) which are generally much smaller than the entire device. NOR-type flash allows a single machine word (byte) to be written – to an erased location – or read independently. The NAND type operates primarily in memory cards , USB flash drives , solid-state drives (those produced in 2009 or later), and similar products, for general storage and transfer o