Computer File - Storing Files

Storing Files

The discussion above describes a file as a concept presented to a user or a high-level operating system. However, any file that has any useful purpose, outside of a thought experiment, must have some physical manifestation. That is, a file (an abstract concept) in a real computer system must have a real physical analogue if it is to exist at all.

In physical terms, most computer files are stored on some type of data storage device. For example, there is a hard disk, from which most operating systems run and on which most store their files. Hard disks have been the ubiquitous form of non-volatile storage since the early 1960s. Where files contain only temporary information, they may be stored in RAM. 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. The use of solid state drives is also beginning to rival the hard disk drive.

In Unix-like operating systems, many files have no direct association with a physical storage device: /dev/null is a prime example, as are just about all files under /dev, /proc and /sys. These can be accessed as files in user space. They are really virtual files that exist, in reality, as objects within the operating system kernel.