 Other features included an enhanced battery @-@ saving capability called persistent storage capability . Previously up to 50 % ( enough for 72 hours of storage ) of battery power was reserved just to maintain data in volatile RAM . This continued the trend of Windows @-@ based devices moving from using RAM as their primary storage medium to the use of a combination of RAM and flash memory ( in use , no distinction between the two is obvious to users ) . Programs and frequently accessed data run in RAM , while most storage is in the flash memory . The OS seamlessly moves data between the two as needed . Everything is backed up in the flash memory , so unlike prior devices , WM5 devices lose no data if power is lost . New to 5 @.@ 0 , OS updates were released as Adaptation kit upgrades , with AKU 3 @.@ 5 being the final released . 
