Filename

A filename (or file name) is a name used to uniquely identify a computer file stored in a file system.

Description

Different file systems impose different restrictions on filename lengths and the allowed characters within filenames.

A filename may include one or more of these components:

host (or node or server) – network device that contains the file
device (or drive) – hardware device or drive
directory (or path) – directory tree (e.g., /usr/bin, \TEMP, [USR.LIB.SRC], etc.)
file – base name of the file
type (format or extension) – indicates the content type of the file (e.g. .txt, .exe, .COM, etc.)
version – revision or generation number of the file

The components required to identify a file varies across operating systems, as does the syntax and format for a valid filename.

Discussions of filenames are complicated by a lack of standardisation of the term.

Sometimes "filename" is used to mean the entire name, such as the Windows name c:\directory\myfile.txt.

Sometimes, it will be used to refer to the components, so the filename in this case would be myfile.txt.

Sometimes, it is a reference that excludes an extension, so the filename would be just myfile.

Such ambiguity is widespread and this article does not attempt to define any one meaning, and indeed may be using any of these meanings.

Some systems will adopt their own standardized nomenclature like "path name" but these too are not standardized across systems.