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.
Multi-level cell (MLC) devices, including triple-level cell (TLC) devices, can store more than one bit per cell.
The floating gate may be conductive (typically polysilicon in most kinds of flash memory) or non-conductive (as in SONOS flash memory).
Once the FG is charged, the electrons in it screen (partially cancel) the electric field from the CG, thus, increasing the threshold voltage (V), and hence, a logical "1" is stored in the gate.
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.
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 of data.
NAND or NOR flash memory is also often used to store configuration data in numerous digital products, a task previously made possible by EEPROM or battery-powered static RAM.