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a cutting tool with rows of cutting teeth along the working surfaces (planes or edges). The first files date from the early Iron Age (Hallstatt culture, c. 900–400 B.C.) and were one of the tools used by iron forgers. The instrument became widespread after the emergence of specialists in metalworking (ancient Rome). Files originally had parallel cutting ridges; later they acquired intersecting ridges. (Such files first appeared in Rus’ in the 12th century.) The following files are distinguished: bastard files (coarse cut), smooth-cut files (fine cut), and barette files (finest cut). Small files with fine cut are usually called needle files.
The cross sections of files may be rectangular, semicircular, triangular, or square. Rasps, files with separate points, are used for working wood and other nonmetallic materials. Files are used manually or mounted on special filing machines.
The history of computing is rich in varied kinds of files and file systems, whether ornate like the Macintosh file system or deficient like many simple pre-1980s file systems that didn't have directories. However, a typical file has these characteristics:
* It is a single sequence of bytes (but consider Macintosh resource forks).
* It has a finite length, unlike, e.g., a Unix device.
* It is stored in a non-volatile storage medium (but see ramdrive).
* It exists (nominally) in a directory.
* It has a name that it can be referred to by in file operations, possibly in combination with its path.
Additionally, a file system may support other file attributes, such as permissions; timestamps for creation, last modification, and last access and revision numbers (a` la VMS).
fileA collection of bytes stored as an individual entity on the computer's hard drive or SSD. A file is the common denominator of storage. All data and programs, no matter which kind, are stored as files with an assigned file name that must be unique within the disk folder (directory) it resides in. Files with the same name can reside in separate folders. See folder.
Computers Know Nothing About Data Files
To the computer, a data file is nothing more than a string of bytes that is identified by name and location on the disk. Once read into the computer's memory, the structure of a file is known to the software that manipulates it. For example, database files are made up of a series of records (one per customer, vendor, transaction, etc.). Word processing files contain a continuous flow of text interspersed with format codes (tags). To learn more about file structures, see database.
Except for ASCII text files, which contain only raw text, other data files have proprietary structures. Formatting and descriptive information are contained in headers at the beginning of the file and/or in tags interspersed throughout the file.
Computers Are Savvy About Program Files
In contrast to data files, the computer is very aware of the content of an executable program file, which contains instructions. When given the starting point of an instruction in memory, the computer expects to find the strings of bytes in a machine instruction format that it recognizes and is able to follow, one instruction after the other (see machine language).
Following are the major file types. See file association, ASCII file, file system and files vs. folders.