Editing Colon (punctuation) (section)

===Addresses===
Internet URLs use the colon to separate the protocol (such as {{code|http:}}) from the [[hostname]] or [[IP address]].{{Ref RFC|3986|repeat=yes}}

In an [[IPv6 address#Representation|IPv6 address]], colons (and one optional double colon) separate up to 8 groups of 16 [[bit]]s in [[hexadecimal]] representation.{{Ref RFC|4291}} In a [[URL]], a colon follows the initial scheme name (such as Hypertext Transfer Protocol ([[HTTP]]) and [[File Transfer Protocol]] (FTP), and separates a [[port number]] from the [[hostname]] or [[IP address]].{{Ref RFC|3986}}

In [[Microsoft Windows]] [[filename]]s, the colon is reserved for use in [[fork (file system)#Microsoft|alternate data streams]] and cannot appear in a filename.<ref>{{cite web |url=https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/ffb795f3-027d-4a3c-997d-3085f2332f6f |title=[MS-FSCC]: 2.1.5 Pathname |website=Microsoft Docs |publisher=Microsoft |date=24 August 2020 |archive-date=22 October 2020 |archive-url=https://archive.today/20201022102028/https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/ffb795f3-027d-4a3c-997d-3085f2332f6f |url-status=live}}</ref> It was used as the directory separator in [[Classic Mac OS]], and was difficult to use in early versions of the newer [[BSD]]-based [[macOS]] due to code swapping the slash and colon to try to preserve this usage. In most systems it is often difficult to put a colon in a filename as the shell interprets it for other purposes.

[[CP/M]] and early versions of [[MSDOS]] required the colon after the names of devices, such as {{code|CON:}} though this gradually disappeared except for disks (where it had to be between the disk name and the required [[path (computing)|path representation]] of the file as in <code>C:\Windows\</code>). This then migrated to use in [[Uniform Resource Locator|URLs]].{{Ref RFC|3986|repeat=yes}}