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where are saved files stored in a computer
Most computer files are stored on some type of data storage device.
What is an example of a data storage device?
For example, most operating systems store files on a hard disk.
What's a hard disk?
A hard disk is an electro-mechanical data storage device that uses magnetic storage to store and retrieve digital data.
Where else can digital data be stored, besides hard disks?
Computer files can be also stored on other media in some cases, such as magnetic tapes, compact discs, Digital Versatile Discs, Zip drives, USB flash drives, etc.

Question: what's the second type of drive in the answer
Self-contained rewrite: What's a USB flash drive?