Editing Filename (section)

==History==

During the 1970s, some [[mainframe]] and [[minicomputers]] had operating systems where files on the system were identified by a user name, or account number.

For example, on the [[TOPS-10]] and [[RSTS/E]] operating systems from [[Digital Equipment Corporation]], files were identified by
* optional device name (one or two characters) followed by an optional unit number, and a colon ":". If not present, it was presumed to be SY:
* the account number, consisting of a bracket "[", a pair of numbers separated by a comma, and followed by a close bracket "]". If omitted, it was presumed to be yours.
* mandatory file name, consisting of 1 to 6 characters (upper-case letters or digits)
* optional 3-character extension.

On the [[OS/360 and successors|OS/360 and successor]] operating systems from [[IBM]], a file name can be up to 44 characters, consisting of upper case letters, digits, and the period; a file name had to start with a letter or number, a period must occur at least once each 8 characters, two consecutive periods can not appear in the name, and the name must end with a letter or digit.<ref>{{cite book |url=https://bitsavers.org/pdf/ibm/360/os/R01-08/C28-6535-0_OS360_Concepts_and_Facilities_1965.pdf |title=IBM Operating System/360 Concepts and Facilities |page=23 |publisher=IBM |id=C28-6535-0 |date=1965}}</ref><ref name="44_char">{{cite web|title=Data Set Naming Rules |work=z/OS TSO/E User's Guide |publisher=IBM |url=https://www.ibm.com/docs/en/zos/3.1.0?topic=conventions-data-set-naming-rules}}</ref> By convention, when using [[Time Sharing Option|TSO]], the letters and numbers before the first period is the account number of the owner or the project it belongs to, but there is no requirement to use this convention.<ref>{{cite web|title=Data Set Naming Conventions |work=z/OS TSO/E User's Guide |publisher=IBM |url=https://www.ibm.com/docs/en/zos/3.1.0?topic=conventions-data-set-naming}}</ref>

On the McGill University [[MUSIC/SP]] system, file names consisted of
* Optional account number, which was one to four characters followed by a colon.If the account number was missing, it was presumed to be in your account, but if it was not, it was presumed to be in the *COM: pseudo-account, which is where all files marked as public were catalogued.
* 1–17 character file name, which could be upper case letters or digits, and the period, with the requirement it not begin or end with a period, or have two consecutive periods.

The Univac [[VS/9]] operating system had file names consisting of 
*Account name, consisting of a dollar sign "$", a 1-7 character (letter or digit) username, and a period ("."). If not present it was presumed to be in your account, but if it was not, the operating system would look in the system manager's account $TSOS. If you typed in a dollar sign only as the account, this would indicate the file was in the $TSOS account ''unless'' the first 1–7 character of the file name before the first period matched an actual account name, then that account was used, e.g. ABLE.BAKER is a file in your account, but if not there the system would search for $TSOS.ABLE.BAKER, but if $ABLE.BAKER was specified, the file $TSOS.ABLE.BAKER would be used ''unless'' $ABLE was a valid account, then it would look for a file named BAKER in that account.
* File name, 1–56 characters (letters and digits) separated by periods. File names cannot start or end with a period, nor can two consecutive periods appear.

In 1985, {{IETF RFC|959}} officially defined a ''pathname'' to be the character string that must be entered into a file system by a user in order to identify a file.<ref>{{cite IETF|rfc=959|title=File Transfer Protocol (FTP)}}</ref>

On early [[personal computer]]s using the [[CP/M]] operating system, filenames were always 11 characters. This was referred to as the [[8.3 filename]] with a maximum of an 8 byte name and a maximum of a 3 byte extension. Utilities and applications allowed users to specify filenames without trailing spaces and include a dot before the extension.  The dot was not actually stored in the directory. Using only 7 bit characters allowed several [[file attributes]] to be included in the actual filename by using the high-order-bit; these attributes included Readonly, Archive, and System.<ref>{{cite web | url=https://www.cpm8680.com/cpmtools/cpm.htm | title=CPM - CP/M disk and file system format }}</ref> Eventually this was too restrictive and the number of characters allowed increased. The attribute bits were moved to a special block of the file including additional information.{{citation needed|date=October 2023}}

The original [[File Allocation Table]] (FAT) file system, used by [[Standalone Disk BASIC-80]], had a 6.3 file name, with a maximum of 6 bytes in the name and a maximum of 3 bytes in the extension.  The [[FAT12]] and [[FAT16]] file systems in [[IBM PC DOS]]/[[MS-DOS]] and [[Microsoft Windows]] prior to [[Windows 95]] used the same 8.3 convention as the CP/M file system.  The FAT file systems supported 8-bit characters, allowing them to support non-ASCII characters in file names, and stored the attributes separately from the file name.

Around 1995, [[VFAT]], an extension to the MS-DOS FAT filesystem, was introduced in [[Windows 95]] and [[Windows NT]]. It allowed mixed-case [[long filename]]s (LFNs), using [[Unicode]] characters, in addition to classic "8.3" names.