File system - Revision history

Jnc: +Cat

2025-04-18T16:04:40Z

+Cat

← Older revision		Revision as of 16:04, 18 April 2025
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	[[Category: OS Basics]]		[[Category: OS Basics]]
			[[Category: File Systems]]

Vaxorcist: /* See also */ Link to ODS-2 added

2023-03-26T07:48:26Z

Jnc: clarify

2022-04-21T05:16:27Z

clarify

← Older revision		Revision as of 05:16, 21 April 2022
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	The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by allocating enough of them to hold a [[file]] of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free [[list]]s, free [[array]]s, etc).		The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by allocating enough of them to hold a [[file]] of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free [[list]]s, free [[array]]s, etc).

	A file system also normally includes [[directory\|directories]], which ~~are collections~~ of ~~related~~ files. Modern file systems are usually a tree-structured [[hierarchy]]; i.e. a directory can also include other directories, the whole being structured as a [[tree]] descending from a '''root directory'''.		A file system also normally includes [[directory\|directories]], which give the names of the files. Modern file systems are usually a tree-structured [[hierarchy]]; i.e. a directory can also include other directories, the whole being structured as a [[tree]] descending from a '''root directory'''.

	==Operations provided==		==Operations provided==
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	Originally, the information as to which blocks were part of a file was kept in the directory; this approach was used in early operating systems such as [[Compatible Time-Sharing System\|CTSS]] and [[TOPS-10]], as well as later ones like [[Multics]] and [[Windows]].		Originally, the information as to which blocks were part of a file was kept in the directory; this approach was used in early operating systems such as [[Compatible Time-Sharing System\|CTSS]] and [[TOPS-10]], as well as later ones like [[Multics]] and [[Windows]].

	[[UNIX]] started a new approach, in which most information about a file (particularly, which blocks were used to hold it) was kept in a separate structure (called an [[inode]] in UNIX); directories (usually implemented as an abstraction on top of the ~~previous~~ layer) only held mappings from file-names (visible to users) to inode numbers.		[[UNIX]] started a new approach, in which most information about a file (particularly, which blocks were used to hold it) was kept in a separate structure (called an [[inode]] in UNIX); directories (usually implemented as an abstraction on top of the file layer) only held mappings from file-names (visible to users) to inode numbers.

	==See also==		==See also==

Jnc: promote dirs

2022-04-20T10:06:34Z

promote dirs

← Older revision		Revision as of 10:06, 20 April 2022
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	A '''file system''' is an abstraction provided by an [[operating system]] to users for them to store data aggregates of all sorts ([[program]] [[source code]], [[executable binary]], document source and formatted output, etc, etc), using names for them which make sense to the users. The actual storage itself typically uses [[secondary storage]] (generally [[disk]]).		A '''file system''' is an abstraction provided by an [[operating system]] to users for them to store data aggregates of all sorts ([[program]] [[source code]], [[executable binary]], document source and formatted output, etc, etc), using names for them which make sense to the users. The actual storage itself typically uses [[secondary storage]] (generally [[disk]]).

	The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by allocating enough of them to hold a [[file]] of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free ~~lists~~, free ~~arrays~~, etc).		The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by allocating enough of them to hold a [[file]] of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free [[list]]s, free [[array]]s, etc).

	A file system also normally includes ~~'''~~directories~~'''~~, which are collections of related files. Modern file systems are usually a tree-structured [[hierarchy]]; i.e. a directory can also include other directories, the whole being structured as a tree descending from a '''root directory'''.		A file system also normally includes [[directory\|directories]], which are collections of related files. Modern file systems are usually a tree-structured [[hierarchy]]; i.e. a directory can also include other directories, the whole being structured as a [[tree]] descending from a '''root directory'''.

	==Operations provided==		==Operations provided==
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	Two main approaches have been used to organize file systems internally.		Two main approaches have been used to organize file systems internally.

	Originally, the information as to which blocks were part of a file was kept in the directory~~, along with other meta-information about the file (date last modified, etc)~~; this approach was used in early operating systems such as [[~~Multics~~]], as well as later ones like [[Windows]].		Originally, the information as to which blocks were part of a file was kept in the directory; this approach was used in early operating systems such as [[Compatible Time-Sharing System\|CTSS]] and [[TOPS-10]], as well as later ones like [[Multics]] and [[Windows]].

	[[UNIX]] started a new approach, in which most information about a file (particularly, which blocks were used to hold it) was kept in a separate structure (called an [[inode]] in UNIX); directories (usually implemented as an abstraction on top of the previous layer) only held mappings from file-names (visible to users) to inode numbers.		[[UNIX]] started a new approach, in which most information about a file (particularly, which blocks were used to hold it) was kept in a separate structure (called an [[inode]] in UNIX); directories (usually implemented as an abstraction on top of the previous layer) only held mappings from file-names (visible to users) to inode numbers.

Jnc: +links

2020-05-29T12:11:34Z

+links

← Older revision		Revision as of 12:11, 29 May 2020
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	A '''file system''' is an abstraction provided by an [[operating system]] to users for them to store data aggregates of all sorts (program source, [[executable binary]], document source and formatted output, etc, etc), using names for them which make sense to the users. The actual storage itself typically uses [[secondary storage]] (generally [[disk]]).		A '''file system''' is an abstraction provided by an [[operating system]] to users for them to store data aggregates of all sorts ([[program]] [[source code]], [[executable binary]], document source and formatted output, etc, etc), using names for them which make sense to the users. The actual storage itself typically uses [[secondary storage]] (generally [[disk]]).

	The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by allocating enough of them to hold a [[file]] of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free lists, free arrays, etc).		The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by allocating enough of them to hold a [[file]] of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free lists, free arrays, etc).

Jnc: +cat

2018-12-16T21:22:31Z

+cat

← Older revision		Revision as of 21:22, 16 December 2018
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	* [[UNIX file system]]		* [[UNIX file system]]
	* [[BSD Fast File System]]		* [[BSD Fast File System]]

			[[Category: OS Basics]]

Jnc: Link hierarchy

2018-10-31T14:52:33Z

Link hierarchy

← Older revision		Revision as of 14:52, 31 October 2018
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	The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by allocating enough of them to hold a [[file]] of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free lists, free arrays, etc).		The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by allocating enough of them to hold a [[file]] of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free lists, free arrays, etc).

	A file system also normally includes '''directories''', which are collections of related files. Modern file systems are usually tree-structured; i.e. a directory can also include other directories, the whole being structured as a tree descending from a '''root directory'''.		A file system also normally includes '''directories''', which are collections of related files. Modern file systems are usually a tree-structured [[hierarchy]]; i.e. a directory can also include other directories, the whole being structured as a tree descending from a '''root directory'''.

	==Operations provided==		==Operations provided==

Jnc: /* Operations provided */ one more

2017-09-24T21:11:02Z

Operations provided: one more

← Older revision		Revision as of 21:11, 24 September 2017
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	* reading and writing them;		* reading and writing them;
	* moving to a different position in a file prior to reading/writing;		* moving to a different position in a file prior to reading/writing;
	* creating new files, and deleting existing ones.		* creating new files, and deleting existing ones;
			* moving a file to a new location.

	==Approaches==		==Approaches==

Jnc: Add typical operations provided

2017-09-23T21:56:50Z

Add typical operations provided

← Older revision		Revision as of 21:56, 23 September 2017
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	A '''file system''' is an abstraction provided by an [[operating system]] to users for them to store data aggregates of all sorts (program source, [[executable binary]], document source and formatted output, etc, etc), using names for them which make sense to the users. The actual storage itself typically uses [[secondary storage]] (generally [[disk]]).		A '''file system''' is an abstraction provided by an [[operating system]] to users for them to store data aggregates of all sorts (program source, [[executable binary]], document source and formatted output, etc, etc), using names for them which make sense to the users. The actual storage itself typically uses [[secondary storage]] (generally [[disk]]).

	The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by ~~allocates~~ enough of them to hold a file of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free lists, free arrays, etc).		The file system takes the actual storage blocks (normally identified with a block number) on a disk, and starts by allocating enough of them to hold a [[file]] of the desired size, and then makes a record of which blocks belong to which files. It also has to know which blocks are 'free', and available for allocation - a variety of data structures are used to hold this information (free lists, free arrays, etc).

	A file system also normally includes '''directories''', which are collections of related files. Modern file systems are usually tree-structured; i.e. a directory can also include other directories, the whole being structured as a tree descending from a '''root directory'''.		A file system also normally includes '''directories''', which are collections of related files. Modern file systems are usually tree-structured; i.e. a directory can also include other directories, the whole being structured as a tree descending from a '''root directory'''.

			==Operations provided==

			The typical operations provided by the operating system include:

			* opening and closing files;
			* reading and writing them;
			* moving to a different position in a file prior to reading/writing;
			* creating new files, and deleting existing ones.

	==Approaches==		==Approaches==

	Two main approaches have been used to organize file systems.		Two main approaches have been used to organize file systems internally.

	Originally, the information as to which blocks were part of a file was kept in the directory, along with other meta-information about the file (date last modified, etc); this approach was used in early operating systems such as [[Multics]], as well as later ones like [[Windows]].		Originally, the information as to which blocks were part of a file was kept in the directory, along with other meta-information about the file (date last modified, etc); this approach was used in early operating systems such as [[Multics]], as well as later ones like [[Windows]].

Jnc: Do a proper 'see also'

2017-08-07T19:45:56Z

Do a proper 'see also'

← Older revision		Revision as of 19:45, 7 August 2017
Line 11:		Line 11:
	Originally, the information as to which blocks were part of a file was kept in the directory, along with other meta-information about the file (date last modified, etc); this approach was used in early operating systems such as [[Multics]], as well as later ones like [[Windows]].		Originally, the information as to which blocks were part of a file was kept in the directory, along with other meta-information about the file (date last modified, etc); this approach was used in early operating systems such as [[Multics]], as well as later ones like [[Windows]].

	[[UNIX]] started a new approach, in which most information about a file (particularly, which blocks were used to hold it) was kept in a separate structure (called an [[inode]] in UNIX); directories (usually implemented as an abstraction on top of the previous layer) only held mappings from file-names (visible to users) to inode numbers. ~~(More information about UNIX file-systems can be found~~ [[UNIX file system~~\|here~~]].)		[[UNIX]] started a new approach, in which most information about a file (particularly, which blocks were used to hold it) was kept in a separate structure (called an [[inode]] in UNIX); directories (usually implemented as an abstraction on top of the previous layer) only held mappings from file-names (visible to users) to inode numbers.

			==See also==

			* [[UNIX file system]]
			* [[BSD Fast File System]]

← Older revision		Revision as of 07:48, 26 March 2023
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	* [[UNIX file system]]		* [[UNIX file system]]
	* [[BSD Fast File System]]		* [[BSD Fast File System]]
			* [[On-disk Structure 2]]

	[[Category: OS Basics]]		[[Category: OS Basics]]