NAND flash memory is a type of non-volatile storage technology that does not require power to retain data.Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. NAND flash architecture was introduced by Toshiba in 1989. There are two types of flash memory, NAND and NOR. The names refer to the type of logic gate used in each memory cell. The NAND type is primarily used in memory cards, USB flash drives, solid-state drives, and similar products, for general storage and transfer of data. The NOR type is used as a replacement for the older EPROM and as an alternative to certain kinds of ROM applications. However, NOR flash memory may emulate ROM primarily at the machine code. NAND or NOR flash memory is also often used to store configuration data in numerous digital products, a task previously made possible by EEPROMs or battery-powered static RAM. NOR and NAND flash differs in two important ways: 1. The connections of the individual memory cells are different. 2. The interface provided for reading and writing the memory is different (NOR allows random-access for reading, NAND allows only page access). NOR and NAND flash get their names from the structure of the interconnections between memory cells. In NOR flash, cells are connected in parallel to the bit lines, allowing cells to be read and programmed individually. The parallel connection of cells resembles the parallel connection of transistors in a CMOS NOR gate. In NAND flash, cells are connected in series, resembling a NAND gate. The series connections consume less space than parallel ones, reducing the cost of NAND flash. It does not, by itself, prevent NAND cells from being read and programmed individually. Flash memory stores information in an array of memory cells made from floating-gate transistors. In traditional SLC devices, each cell stores only one bit of information. Some newer flash memory, known as MLC devices, can store more than one bit per cell by choosing between multiple levels of electrical charge to apply to the floating gates of its cells.The floating gate may be conductive or non-conductive. NAND flash uses floating-gate transistors, but they are connected in a way that resembles a NAND gate: several transistors are connected in series, and only if all word lines are pulled high is the bit line pulled low. These groups are then connected via some additional transistors to a NOR-style bit line array.NAND flash uses tunnel injection for writing and tunnel release for erasing. NAND flash memory forms the core of the removable USB storage devices known as USB flash drives, as well as most memory card formats and solid-state drives available today. MP3 players, digital cameras and USB drives use NAND flash. NOR flash is faster, but it's also more expensive. NOR type is used mostly in mobile phones.Some devices use both NAND and NOR.NAND is best suited to flash devices requiring high capacity data storage. NAND flash devices offers faster erase, write, and read capabilities over NOR architecture. Author Bio- John Smith is an author of Strontium Technology is a global leader in PC and flash memory cards manufacturing currently based out of Singapore having customer base across Australia, New Zealand, South East Asia, India, US, Canada and Latin America.