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In Unix and operating systems inspired by it, the file system is considered a central component of the operating system. It was also one of the first parts of the system to be designed and implemented by Ken Thompson in the first experimental version of Unix, dated 1969.〔 Like in other operating systems, the filesystem provides information storage and retrieval, as well as interprocess communication, in the sense that the many small programs that traditionally comprise a Unix system can store information in files so that other programs can read these, although pipes complemented it in this role starting with the Third Edition. Additionally, the filesystem provides access to other resources through so-called ''device files'' that are entry points to terminals, printers, and mice. The rest of this article uses "Unix" as a generic name to refer to both the original Unix operating system as well as its many workalikes. ==Principles== The filesystem appears as a single rooted tree of directories.〔 Instead of addressing separate volumes such as disk partitions, removable media, and network shares as separate trees (as done in MS-DOS and Windows: each "drive" has a drive letter that denotes the root of its file system tree), such volumes can be "mounted" on a directory, causing the volume's file system tree to appear as that directory in the larger tree.〔 The root of the entire tree is denoted /.In the original Bell Labs Unix, a two-disk setup was customary, where the first disk contained startup programs, while the second contained users' files and programs. This second disk was mounted at the empty directory named usr on the first disk, causing the two disks to appear as one filesystem, with the second's disks contents viewable at /usr.Unix directories do not "contain" files. Instead, they contain the names of files paired with references to so-called inodes, which in turn contain both the file and its metadata (owner, permissions, time of last access, etc., but no name). Multiple names in the file system may refer to the same file, a feature known as (hard) linking.〔 If this feature is taken into account, the file system is a limited type of directed acyclic graph, although the ''directories'' still form a tree, as they may typically not be hard-linked. (As originally envisioned in 1969, the Unix file system would in fact be used as a general graph with hard links to directories providing navigation, instead of path names.) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Unix filesystem」の詳細全文を読む スポンサード リンク
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