Memory cards are solid-state electronic flash memory storage devices used with cameras, handheld and laptop computers, phones, music players and other electronics.
They offer re-recordability, power-free storage, small form factor and rugged environmental specifications.
|Multi Media Card||MMC||32x24x1.5mm|
|Secure Digital Card||sD||32x24x2.1mm|
|Extreme Digital Card||xD||20x25x1.7mm|
Since all sorts of EEPROM devices only allow a finite number of write cycles, some of these cards incorporate wear levelling algorithms to spread the wear and to avoid wearing out specific places which are often written to.
(I am not sure here) CompactFlash uses wear levelling while SmartMedia does not have any intelligence built in and presents the raw chip on its external interfaces.