Editing Filename extension (section)

{{Short description|Filename suffix that indicates the file's type}}
{{more citations needed|date=November 2015}}
A '''filename extension''', '''file name extension''' or '''file extension''' is a suffix to the [[filename|name]] of a [[computer file]] (for example, <code>[[Text file|.txt]]</code>, <code>[[MP3|.mp3]]</code>, <code>[[.exe]]</code>) that indicates a characteristic of the file contents or its intended use. A filename extension is typically delimited from the rest of the filename with a [[full stop]] (period), but in some systems<ref>{{cite book|title=z/VM 7.2 CMS Primer|id=SC24-6265-01|section=What Is a File?|section-url=https://www.ibm.com/servers/resourcelink/svc0302a.nsf/pages/zVMV7R2sc246265/$file/dmsb2_v7r2.pdf#page=23|page=7|quote=One thing you need to know about creating files with z/VM is that each file needs its own three-part identifier. The first part of the identifier is the file name. The second part is the file type. And the third part is the file mode. These three file identifiers are often abbreviated fn ft fm.|date=2021-12-05|url=https://www.ibm.com/servers/resourcelink/svc0302a.nsf/pages/zVMV7R2sc246265/$file/dmsb2_v7r2.pdf|publisher=IBM}}</ref> it is separated with spaces.

Some [[file system]]s, such as the [[File Allocation Table|FAT]] file system used in [[DOS]], implement filename extensions as a feature of the file system itself and may limit the length and format of the extension, while others, such as [[Unix]] file systems, the [[VFAT]] file system, and [[NTFS]], treat filename extensions as part of the filename without special distinction.