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Flash memory is a kind of electronic memory chip. It is rewritable and does not need a continuous power supply. It is an Electrically-Erasable Programmable Read-Only (EEPROM) and a Non-Volatile Read Write (NVRWM) kind of a memory. Flash memory is used in computers (BIOS chips), MP3 players, video game consoles (memory cards), USB flash drives, mobile phones, and digital cameras (memory chips, CompactFlash or SmartMedia).
Flash memory is generally used in battery-powered devices. Flash memory's non-volatility, fast-read access time, and better shock resistance make it a very good memory tool. Flash memory is a low-cost, high-speed, high-density, low-power, and a highly reliable memory device.
Flash memory was invented in 1984, by Dr. Fujio Masuoka for Toshiba. There are two kinds of flash memory: NOR flash and NAND flash. The first commercial NOR flash chip was designed by Intel in 1988. NOR flash has a complete memory interface with the ability to provide random access to any location. This is ideal for storing program codes that need not be altered frequently. However, NOR flash has longer erase and write times as compared to NAND flash.
NAND flash memory devices were developed by Toshiba and Samsung in 1989. NAND flash is relatively less expensive than NOR flash. It also has faster write and erase times, more endurance, and higher density. However, NAND chips are more suitable for mass-storage devices like memory and PC cards because of their I/O interface that allows only sequential access to data. SmartMedia, MMC, Memory Stick and Secure Data are some of the NAND flash memories.
In a flash memory chip, information is stored in an array of cells or floating gate transistors, which can store one bit of information each. Some advanced cells can store even two bits of information. The capacity of flash memory chips ranges vastly from kilobits to several megabits or even gigabits. Samsung has recently developed a NAND flash memory chip that has a capacity of 16 gigabits. The only limitation of a flash memory is that it can be erased and rewritten only at the block level, rather than the byte level. CompactFlash, Secure Digital, xD, Memory Stick, and Smartmedia are some of the most popular models of flash memory.