A category of memory chips that hold their content without electrical power. Firmware includes rewritable flash memory and EEPROM, reprogrammable PROM and EPROM and read-only ROM technologies. Early firmware chips were low capacity and costly and used only to hold instructions and settings, especially in portable devices. In addition, the content stored in the first chips really was "firm," either read-only (permanent) or reprogrammable with difficulty (see ROM, PROM and EPROM).

Flash memory, the most common firmware, is rewritable, and used like a computer's hard disk. Today's portable devices use gigabytes of flash memory for songs, photos and videos as well as software applications. See memory, flash memory and FOTA.