Filename

Dir command in Windows Command Prompt

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Filename or file name is a name used to uniquely identify a computer file stored in a file system. Different file systems impose different restrictions on filename lengths and the allowed characters within filenames.

Overview

A filename may include one or more of these components:

• Base name: The primary name of the file.
• Extension: A suffix at the end of the filename that indicates the file format or the usage of the file. It is usually separated from the base name by a dot ('.').
• Path: The location of the file within the file system, consisting of a sequence of directory names leading to the file name itself.

Filename Components

Base Name

The base name represents the main identifier for the file. It is what users most frequently use to refer to the file. The base name can include any character supported by the file system, except for the directory separator (such as '/' on UNIX-like systems or '\\' on Windows systems) and characters explicitly disallowed by the file system.

Extension

The extension of a file is typically a two to four-character suffix that specifies the file's type or intended use. Common examples include .txt for plain text files, .jpg for JPEG image files, and .exe for executable programs on Windows. Not all file systems require the use of file extensions.

Path

The path specifies the file's location within the file system's directory structure. It includes the sequence of directories that must be traversed to reach the file, usually ending with the file name itself. Paths can be absolute, specifying a location in relation to the root of the file system, or relative, specifying a location in relation to the current working directory.

File Naming Conventions

File naming conventions vary between operating systems. However, there are some general practices:

• Avoid using special characters that are reserved by the operating system or file system.
• Use file extensions that accurately represent the file type.
• Keep filenames to a reasonable length, though this depends on the file system's limitations.

File Systems and Filename Limitations

Different file systems have different limitations for filenames:

• FAT32: Up to 255 characters, with some reserved characters not allowed.
• NTFS: Up to 255 characters, supports a broader range of characters than FAT32.
• ext3/ext4: Up to 255 bytes for filenames, with no restrictions on the characters used, except for '/' and null character.

See Also

• File system
• Path (computing)
• File format
• Directory (computing)

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