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47-502: Existing members may receive a set number of invitations (sometimes in the form of tokens) to allow others to join the service. Those invited to a website are typically sent either a specialized URL or a single-use pass code. Invitation systems for websites are usually temporary. They are typically used for services in private beta testing , in order to control the number of users on the service. In other cases, they can be used due to limited availability of server resources. There are

94-480: A pathname to be the character string that must be entered into a file system by a user in order to identify a file. On early personal computers 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

141-470: A secure connection to the website . Internet users are distributed throughout the world using a wide variety of languages and alphabets, and expect to be able to create URLs in their own local alphabets. An Internationalized Resource Identifier (IRI) is a form of URL that includes Unicode characters. All modern browsers support IRIs. The parts of the URL requiring special treatment for different alphabets are

188-414: A Fortran compiler might use the extension FOR for source input file, OBJ for the object output and LST for the listing. Although there are some common extensions, they are arbitrary and a different application might use REL and RPT . Extensions have been restricted, at least historically on some systems, to a length of 3 characters, but in general can have any length, e.g., html . There

235-401: 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. Eventually this was too restrictive and the number of characters allowed increased. The attribute bits were moved to a special block of

282-566: A file: additionally, the exact byte representation of the filename on the storage device is needed. This can be solved at the application level, with some tricky normalization calls. The issue of Unicode equivalence is known as "normalized-name collision". A solution is the Non-normalizing Unicode Composition Awareness used in the Subversion and Apache technical communities. This solution does not normalize paths in

329-456: A filename, although most utilities do not handle them well. Filenames may include things like a revision or generation number of the file, a numerical sequence number (widely used by digital cameras through the DCF standard ), a date and time (widely used by smartphone camera software and for screenshots ), or a comment such as the name of a subject or a location or any other text to help identify

376-406: A filesystem to storing components of names, so increasing limits often requires an incompatible change, as well as reserving more space. A particular issue with filesystems that store information in nested directories is that it may be possible to create a file with a complete pathname that exceeds implementation limits, since length checking may apply only to individual parts of the name rather than

423-440: A growing number of sites which use invitation systems on a permanent basis to create exclusivity and to control quality of user-generated content . Rarely, they may be used on a permanent basis in order to aggregate social network statistics (all users will ultimately have a traceable connection to all others). They are sometimes used to avoid abusive types or spammers , by relying on mutual trust between all members. Sometimes,

470-421: A maximum of eight plus three characters was a filename alias of " long file name.??? " as a way to conform to 8.3 limitations for older programs. This property was used by the move command algorithm that first creates a second filename and then only removes the first filename. Other filesystems, by design, provide only one filename per file, which guarantees that alteration of one filename's file does not alter

517-582: A period must occur at least once each 8 characters, two consecutive periods could not appear in the name, and must end with a letter or digit. By convention, the letters and numbers before the first period was the account number of the owner or the project it belonged to, but there was no requirement to use this convention. On the McGill University MUSIC/SP system, file names consisted of The Univac VS/9 operating system had file names consisting of In 1985, RFC   959 officially defined

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564-447: A tiered invitation system may be in place, wherein those higher up the hierarchy will have the power to grant more invitations, whereas low-ranking members may receive few or even no invitation rights. Some prominent services which were once invitation-based include blog -host LiveJournal , social network Yahoo 360° , and podcast publisher Odeo . When Google releases new services, an invitation requirement has often been imposed for

611-437: Is empty if it has no characters; the scheme component is always non-empty. The authority component consists of subcomponents : This is represented in a syntax diagram as: [REDACTED] The URI comprises: A web browser will usually dereference a URL by performing an HTTP request to the specified host, by default on port number 80. URLs using the https scheme require that requests and responses be made over

658-416: Is a specific type of Uniform Resource Identifier (URI), although many people use the two terms interchangeably. URLs occur most commonly to reference web pages ( HTTP / HTTPS ) but are also used for file transfer ( FTP ), email ( mailto ), database access ( JDBC ), and many other applications. Most web browsers display the URL of a web page above the page in an address bar . A typical URL could have

705-606: Is no general encoding standard for filenames. File names have to be exchanged between software environments for network file transfer, file system storage, backup and file synchronization software, configuration management, data compression and archiving, etc. It is thus very important not to lose file name information between applications. This led to wide adoption of Unicode as a standard for encoding file names, although legacy software might not be Unicode-aware. Traditionally, filenames allowed any character in their filenames as long as they were file system safe. Although this permitted

752-741: Is that different instances of the script or program can use different files. This makes an absolute or relative path composed of a sequence of filenames. Unix-like file systems allow a file to have more than one name; in traditional Unix-style file systems, the names are hard links to the file's inode or equivalent. Windows supports hard links on NTFS file systems, and provides the command fsutil in Windows XP, and mklink in later versions, for creating them. Hard links are different from Windows shortcuts , classic Mac OS/macOS aliases , or symbolic links . The introduction of LFNs with VFAT allowed filename aliases. For example, longfi~1.??? with

799-431: The file type . Some other file systems, such as Unix file systems, VFAT , and NTFS , treat a filename as a single string; a convention often used on those file systems is to treat the characters following the last period in the filename, in a filename containing periods, as the extension part of the filename. Multiple output files created by an application may use the same basename and various extensions. For example,

846-512: The HTML Specification referred to "Universal" Resource Locators. This was dropped some time between June 1994 ( RFC  1630 ) and October 1994 (draft-ietf-uri-url-08.txt). In his book Weaving the Web , Berners-Lee emphasizes his preference for the original inclusion of "universal" in the expansion rather than the word "uniform", to which it was later changed, and he gives a brief account of

893-469: The IETF Living Documents birds of a feather session in 1992. The format combines the pre-existing system of domain names (created in 1985) with file path syntax, where slashes are used to separate directory and filenames . Conventions already existed where server names could be prefixed to complete file paths, preceded by a double slash ( // ). Berners-Lee later expressed regret at

940-455: The Unicode version in use. For instance, UDF is limited to Unicode 2.0; macOS's HFS+ file system applies NFD Unicode normalization and is optionally case-sensitive (case-insensitive by default.) Filename maximum length is not standard and might depend on the code unit size. Although it is a serious issue, in most cases this is a limited one. On Linux, this means the filename is not enough to open

987-516: 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 filenames (LFNs), using Unicode characters, in addition to classic "8.3" names. Programs and devices may automatically assign names to files such as a numerical counter (for example IMG_0001.JPG ) or a time stamp with

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1034-424: The clock of their camera. Internet-connected devices such as smartphones may synchronize their clock from a NTP server. An absolute reference includes all directory levels. In some systems, a filename reference that does not include the complete directory path defaults to the current working directory . This is a relative reference. One advantage of using a relative reference in program configuration files or scripts

1081-452: The contention that led to the change. Every HTTP URL conforms to the syntax of a generic URI. The URI generic syntax consists of five components organized hierarchically in order of decreasing significance from left to right: A component is undefined if it has an associated delimiter and the delimiter does not appear in the URI; the scheme and path components are always defined. A component

1128-459: The current date and time. The benefit of a time stamped file name is that it facilitates searching files by date, given that file managers usually feature file searching by name. In addition, files from different devices can be merged in one folder without file naming conflicts. Numbered file names, on the other hand, do not require that the device has a correctly set internal clock. For example, some digital camera users might not bother setting

1175-644: The domain name and path. The domain name in the IRI is known as an Internationalized Domain Name (IDN). Web and Internet software automatically convert the domain name into punycode usable by the Domain Name System ; for example, the Chinese URL http://例子.卷筒纸 becomes http://xn--fsqu00a.xn--3lr804guic/ . The xn-- indicates that the character was not originally ASCII . The URL path name can also be specified by

1222-474: The encoding used for a filename as part of the extended file information. This forced costly filename encoding guessing with each file access. A solution was to adopt Unicode as the encoding for filenames. In the classic Mac OS, however, encoding of the filename was stored with the filename attributes. The Unicode standard solves the encoding determination issue. Nonetheless, some limited interoperability issues remain, such as normalization (equivalence), or

1269-476: The entire name. Many Windows applications are limited to a MAX_PATH value of 260, but Windows file names can easily exceed this limit. From Windows 10, version 1607 , MAX_PATH limitations have been removed. Filenames in some file systems, such as FAT and the ODS-1 and ODS-2 levels of Files-11 , are composed of two parts: a base name or stem and an extension or suffix used by some applications to indicate

1316-670: The exact capitalization by which it is named. On a case-insensitive, case-preserving file system, on the other hand, only one of "MyName.Txt", "myname.txt" and "Myname.TXT" can be the name of a file in a given directory at a given time, and a file with one of these names can be referenced by any capitalization of the name. From its original inception, the file systems on Unix and its derivative systems were case-sensitive and case-preserving. However, not all file systems on those systems are case-sensitive; by default, HFS+ and APFS in macOS are case-insensitive but case-preserving, and SMB servers usually provide case-insensitive behavior (even when

1363-623: The file including additional information. 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

1410-515: The file. Some people use the term filename when referring to a complete specification of device, subdirectories and filename such as the Windows C:\Program Files\Microsoft Games\Chess\Chess.exe . The filename in this case is Chess.exe . Some utilities have settings to suppress the extension as with MS Windows Explorer. During the 1970s, some mainframe and minicomputers had operating systems where files on

1457-434: The first few months of the service's existence, including email provider Gmail , social networking service Orkut and real-time collaboration site Google Wave . Many BitTorrent trackers , known as "private trackers", use an invitation system in order to maintain torrent quality, speeds, and safety. Demonoid and ImmortalSeed are examples of invitation-only trackers. Despite its invitation-only status, Oink's Pink Palace

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1504-578: The form http://www.example.com/index.html , which indicates a protocol ( http ), a hostname ( www.example.com ), and a file name ( index.html ). Uniform Resource Locators were defined in RFC   1738 in 1994 by Tim Berners-Lee , the inventor of the World Wide Web , and the URI working group of the Internet Engineering Task Force (IETF), as an outcome of collaboration started at

1551-454: The introduction of VFAT , store filenames as upper-case regardless of the letter case used to create them. For example, a file created with the name "MyName.Txt" or "myname.txt" would be stored with the filename "MYNAME.TXT" (VFAT preserves the letter case). Any variation of upper and lower case can be used to refer to the same file. These kinds of file systems are called case-insensitive and are not case-preserving . Some filesystems prohibit

1598-415: The new Unicode encoding. Mac OS X 10.3 marked Apple's adoption of Unicode 3.2 character decomposition, superseding the Unicode 2.1 decomposition used previously. This change caused problems for developers writing software for Mac OS X. Within a single directory, filenames must be unique. Since the filename syntax also applies for directories, it is not possible to create a file and directory entries with

1645-823: The other filename's file. Some filesystems restrict the length of filenames. In some cases, these lengths apply to the entire file name, as in 44 characters in IBM z/OS . In other cases, the length limits may apply to particular portions of the filename, such as the name of a file in a directory, or a directory name. For example, 9 (e.g., 8-bit FAT in Standalone Disk BASIC ), 11 (e.g. FAT12 , FAT16 , FAT32 in DOS), 14 (e.g. early Unix), 21 ( Human68K ), 31, 30 (e.g. Apple DOS 3.2 and 3.3), 15 (e.g. Apple ProDOS ), 44 (e.g. IBM S/370), or 255 (e.g. early Berkeley Unix) characters or bytes. Length limits often result from assigning fixed space in

1692-432: The protocol of the current page, typically HTTP or HTTPS. Filename A filename or file name is a name used to uniquely identify a computer file in a file system . Different file systems impose different restrictions on filename lengths. A filename may (depending on the file system) include: The components required to identify a file by utilities and applications varies across operating systems, as does

1739-482: The repository. Paths are only normalized for the purpose of comparisons. Nonetheless, some communities have patented this strategy, forbidding its use by other communities. To limit interoperability issues, some ideas described by Sun are to: Those considerations create a limitation not allowing a switch to a future encoding different from UTF-8. One issue was migration to Unicode. For this purpose, several software companies provided software for migrating filenames to

1786-558: The same character set for composing a filename. Before Unicode became a de facto standard, file systems mostly used a locale-dependent character set. By contrast, some new systems permit a filename to be composed of almost any character of the Unicode repertoire, and even some non-Unicode byte sequences. Limitations may be imposed by the file system, operating system, application, or requirements for interoperability with other systems. Many file system utilities prohibit control characters from appearing in filenames. In Unix-like file systems,

1833-580: The same name in a single directory. Multiple files in different directories may have the same name. Uniqueness approach may differ both on the case sensitivity and on the Unicode normalization form such as NFC, NFD. This means two separate files might be created with the same text filename and a different byte implementation of the filename, such as L"\x00C0.txt" (UTF-16, NFC) (Latin capital A with grave) and L"\x0041\x0300.txt" (UTF-16, NFD) (Latin capital A, grave combining). Some filesystems, such as FAT prior to

1880-514: The syntax and format for a valid filename. The characters allowed in filenames depend on the file system. The letters A–Z and digits 0–9 are allowed by most file systems; many file systems support additional characters, such as the letters a–z, special characters, and other printable characters such as accented letters, symbols in non-Roman alphabets, and symbols in non-alphabetic scripts. Some file systems allow even unprintable characters, including Bell , Null , Return and Linefeed , to be part of

1927-496: 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 On the OS/VS1 , MVS , and OS/390 operating systems from IBM , a file name was up to 44 characters, consisting of upper case letters, digits, and the period. A file name must start with a letter or number,

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1974-439: The underlying file system is case-sensitive, e.g. Samba on most Unix-like systems), and SMB client file systems provide case-insensitive behavior. File system case sensitivity is a considerable challenge for software such as Samba and Wine , which must interoperate efficiently with both systems that treat uppercase and lowercase files as different and with systems that treat them the same. File systems have not always provided

2021-405: The use of any encoding, and thus allowed the representation of any local text on any local system, it caused many interoperability issues. A filename could be stored using different byte strings in distinct systems within a single country, such as if one used Japanese Shift JIS encoding and another Japanese EUC encoding. Conversion was not possible as most systems did not expose a description of

2068-447: The use of dots to separate the parts of the domain name within URIs , wishing he had used slashes throughout, and also said that, given the colon following the first component of a URI, the two slashes before the domain name were unnecessary. Early WorldWideWeb collaborators including Berners-Lee originally proposed the use of UDIs: Universal Document Identifiers. An early (1993) draft of

2115-413: The use of lower case letters in filenames altogether. Some file systems store filenames in the form that they were originally created; these are referred to as case-retentive or case-preserving . Such a file system can be case-sensitive or case-insensitive . If case-sensitive, then "MyName.Txt" and "myname.txt" may refer to two different files in the same directory, and each file must be referenced by

2162-620: The user in the local writing system. If not already encoded, it is converted to UTF-8 , and any characters not part of the basic URL character set are escaped as hexadecimal using percent-encoding ; for example, the Japanese URL http://example.com/引き割り.html becomes http://example.com/%E5%BC%95%E3%81%8D%E5%89%B2%E3%82%8A.html . The target computer decodes the address and displays the page. Protocol-relative links (PRL), also known as protocol-relative URLs (PRURL), are URLs that have no protocol specified. For example, //example.com will use

2209-549: Was accessed by government authorities and forced to close in October 2007. Several actors in the Video game industry are also using this approach. Uniform Resource Locator A uniform resource locator ( URL ), colloquially known as an address on the Web , is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it. A URL

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