A CDE Definition
(1) For Adobe's multimedia authoring and playback system, see Flash.
(2) Flash memory is the most popular non-volatile, rewritable storage chip. Comprised of cells that hold a charge without power, flash memory is extremely durable and used in just about every electronic device, including cameras, smartphones, tablets, music players and USB drives. It is also the storage component in solid state drives (SSDs), which increasingly replace hard drives in computers and servers. All flash memory eventually wears out, but most users will have many years of service (see SSD write cycle). See solid state drive.
Evolving from the EEPROM chip, flash was invented by Toshiba in the mid-1980s and named after its ability to erase a block of data "in a flash." However, this block erasing is its least desirable feature because it adds a step. To change what is stored in flash memory, the cells must first be erased in blocks ranging from 16KB to 512KB in length. Then the cells can be written.
NOR Flash for Execution
NOR flash is used for program execution similar to RAM. Introduced by Intel in 1988, NOR supports one-byte random access, which means a program's instructions are executed directly from the NOR flash the same way computers execute instructions in RAM. Unlike RAM, NOR flash does not require power to hold its content. See computer and RAM.
NAND Flash for Storage
Toshiba developed the less costly NAND flash in 1989. It has denser cells and faster erasing and writing than NOR. For example, in a digital camera, an internal NOR chip holds the software, but the removable memory cards are composed of NAND chips. In a computer, a translation layer makes a NAND flash solid state drive (SSD) function like a hard drive for both program and data storage (see FTL). Just like a hard drive, instructions in a program are first read into RAM and then executed. For more on flash architecture, see EEPROM, NAND flash and MLC. See charge trap flash, USB drive, memory card, solid state drive, flash BIOS, early memories and future memory chips.
From Spinning Platters to Flash
USB Drives "Are" Flash Memory
Memory Cards Are the Camera's "Film"
Disk Pack Storage - 1970s
Flash For Sale
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