Auxiliary memory
（重定向自Auxiliary storage）
![USB flash drives, a type of secondary storage.](/Images/godic/202412/22/SanDisk_Cruzer_Micro4155.png")
![The bottom surface of a compact disc, showing characteristic iridescence.](/Images/godic/202412/22/CD_autolev_crop4155.jpg")
![A hard disk drive with protective cover removed.](/Images/godic/202412/22/Hard_disk_platter_reflection4155.jpg")
Auxiliary memory, also known as auxiliary storage, secondary storage, secondary memory or external memory, is a non-volatile memory (does not lose stored data when the device is powered down) that is not directly accessible by the CPU, because it is not accessed via the input/output channels (it is an external device). In RAM devices (as flash memory) data can be directly deleted or changed.