Computer file

A computer file is a computer resource for recording data discretely in a computer storage device. Just as words can be written to paper, so can information be written to a computer file.

There are different types of computer files, designed for different purposes. A file may be designed to store a picture, a written message, a video, a computer program, or a wide variety of other kinds of data. Some types of files can store different several types of information at once.

By using computer programs, a person can open, read, change, and close a computer file. Computer files may be reopened, modified, and copied an arbitrary number of times.

Typically, computer files are organised in a file system, which keeps track of where the files are, and enables people to access them.

The word "file" was used publicly in the context of computer storage as early as February, 1950. In an RCA (Radio Corporation of America) advertisement in Popular Science Magazine describing a new "memory" vacuum tube it had developed, RCA stated:

In 1952, "file" was used in referring to information stored on punched cards.

In early usage, people regarded the underlying hardware (rather than the contents) as a file. For example, the IBM 350 disk drives were called "disk files". In about 1961 the Burroughs MCP and the MIT Compatible Time-Sharing System introduced the concept of a "file system", which managed several virtual "files" on one storage device, giving the term its present-day meaning. Although the current term "register file" shows the early concept of files, it has largely disappeared.

The word ultimately comes from the Latin filum "a thread".

On most modern operating systems, files are organized into one-dimensional arrays of bytes. The format of a file is defined by its content since a file is solely a container for data, although, on some platforms the format is usually indicated by its filename extension, specifying the rules for how the bytes must be organized and interpreted meaningfully. For example, the bytes of a plain text file (.txt in Windows) are associated with either ASCII or UTF-8 characters, while the bytes of image, video, and audio files are interpreted otherwise. Most file types also allocate a few bytes for metadata, which allows a file to carry some basic information about itself.

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