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 first NAND-based removable media format was Smart Media in 1995, and many others have followed, including: Flash memory stores information in an array of memory cells made from floating-gate transistors.
In single-level cell (SLC) devices, each cell stores only one bit of information.
In flash memory, each memory cell resembles a standard MOSFET, except that the transistor has two gates instead of one.
On top is the control gate (CG), as in other MOS transistors, but below this there is a floating gate (FG) insulated all around by an oxide layer.
Over half the energy used by a 1.8 V NAND flash chip is lost in the charge pump itself.This makes NAND flash unsuitable as a drop-in replacement for program ROM, since most microprocessors and microcontrollers require byte-level random access.In this regard, NAND flash is similar to other secondary data storage devices, such as hard disks and optical media, and is thus highly suitable for use in mass-storage devices, such as memory cards.NOR flash continues to be the technology of choice for embedded applications requiring a discrete non-volatile memory device.The low read latencies characteristic of NOR devices allow for both direct code execution and data storage in a single memory product.In addition to being non-volatile, flash memory offers fast read access times, although not as fast as static RAM or ROM.