non-volatile memory - technical definition

Refers to memory chips that hold their content without power being applied. It may refer to chips that are not changeable, such as ROMs and PROMs, or to chips that can be rewritten many times such as flash memory. Being able to hold instructions and data without power is essential in a myriad of devices because AC power can fail and batteries become depleted. Rewritability is essential in many applications as well.

Although magnetic disks hold their content without power, they are more accurately called "storage devices," rather than non-volatile memory. See memory types for more details. See future memory chips.