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flash memory - Computer Definition
A type of non-volatile read-only memory (ROM) that can store data or programs, be erased, and be used again. Flash memory must be erased in blocks, rather than a byte at a time, which limits its use to applications such as a supplement to or replacement for a mechanical hard disk drive. Flash memory is unsuitable for use as main memory, or random access memory (RAM). See also RAM and ROM.
(1) See also Flash (multimedia authoring and playback system).
(2) The most popular non-volatile, rewritable memory chip. Extremely durable, flash memory is used in just about every electronic device, including USB drives, cameras, iPods, smartphones, tablets, computers and servers. Erase in a Flash! Evolving from the EEPROM chip, flash was invented by Toshiba in the mid-1980s and named after its ability to erase a block of a data "in a flash." Ironically, this block erasing is its least desired feature and one the industry would dearly love to eliminate (see future memory chips). For more about the flash cell architecture, see EEPROM. NOR and NAND NOR flash is like RAM, while NAND is like a hard drive. For example, in a digital camera, an internal NOR chip holds the software, while the removable memory cards are composed of NAND chips. Before any writing can take place, both NOR and NAND cells must be erased in large blocks, typically 128KB in size. See logic gate. NOR for Software First delivered by Intel in 1988, the NOR "linear flash" interface supports one-byte random access, which means a program's instructions stored in NOR flash are copied out and executed the same way computers have fetched instructions from main memory for decades. See memory. NAND for Storage One year after the first NOR chips, Toshiba developed the less costly NAND flash, which has denser cells and faster erasing and writing than NOR. A "flash translation layer" makes NAND flash look like a disk drive to the operating system (see FTL). All flash memory eventually wears out, but in practice, most users will have many years of service (see SSD write cycle). See MLC, charge trap flash, USB drive, memory card, solid state drive, flash BIOS and early memories.