Flash memory is a modern form of erasable memory. Whereas EEPROM was erased in bulk, flash allows more selective erasure.
The concept was developed by Dr. Fujio Masuoka of Toshiba. It was presented at the 1984 IEEE International Electron Devices Meeting, IEDM held in San Francisco, California. Intel introduced the NOR chip in 1988; Toshiba introduced the NAND type chip in 1991.
Most commercially available flash products are guaranteed to withstand between 100,000 and 1,000,000 program/erase cycles.
With NOR flash, the memory cells are connected in parallel enabling the device to have better random access. NAND flash is optimized for density and access is performed in a serial manner. This reduces the amount of access circuitry required. For this reason NOR has traditionally been used for code access and NAND for data access.