The logical organization of the file system
Filetypes File system support for several functionally different types of files,
of which typically is composed of ordinary files, files, directories, special
files, named pipes that are shown in memory of the files and others. Ordinary
files or files that contain the arbitrary nature of the records of the user or
as a result of the system and user programs Most modern operating systems (eg,
UNIX, Windows, OS / 2) does not limit or control the content and The contents of
the file structures are usually determined by a normal file, which it operates.
For example, a text editor create a text file consisting of rows of characters
represented in any code. This may be the documents, the source programs, etc.
Text files can be read on the screen and print. Binaries are not using the codes
of characters, they often have a complex internal structure, such as executable
code or a backup. All operating systems should be able to identify at least one
type of file - their own executable files. Catalog - this is a special type of
file, which contains background information about the system files, grouped by
users on an informal basis of (for example, in one united group files,
containing documents of a treaty, or the files that make up a software package).
In many operating systems to the directory may include files of any type,
including other directories, which is formed by the tree structure, easy to find
catalogs establish a correspondence between file names and characteristics, the
file system to manage files. Those characteristics include, in particular, the
information (or a pointer to another structure that contains the data) on the
type of file and its location on the drive, the file access rights and the dates
of its creation and modification. In all other respects, the file system
directories are treated as ordinary files. Special files - this is bogus files
associated with the input-output devices that are used to unify the mechanism to
access files and external devices. Special files allows users to input / output
operations through normal command entry in the file or reading from a file.
These commands are processed first, file system software, and then at some stage,
the query is converted into the operating system commands the appropriate device.
Modern file systems support and other types of files, such as symbolic
communication, named pipes that are shown in the memory files. They will be
considered later. Hierarchical file system Users to access files on the
character names. However, the ability of human memory limit the number of names
of objects to which the user can turn on the name. Hierarchical namespaces
significantly expand those limits. That is why the majority of file systems have
a hierarchical structure in which the levels are created by the fact that the
directory at a lower level can be included in the directory at a higher level
Graf, describing the hierarchy of folders can be a tree or network. Directories
form a tree, if allowed to enter only the file in a directory, and the network -
if the file can be composed in several directories, for example, in MS-DOS and
Windows directories are a tree-like structure, and in UNIX - the network. In the
tree structure of each file is a leaf. The highest level directory called the
root, or root (root). If such an organization was released from the user to
remember the names of all files, it is about to submit to what the group can be
assigned a file, through a consistent view of directories to find it.
Hierarchical structure is suitable for multi-work: each user with their files in
a directory location or poddereve catalogs, and at the same time, all the files
in the system is logically linked. For this is a one-hierarchical organization,
which includes all the files in a directory Filenames All types of files are
symbolic names. In a hierarchically organized file systems are typically used
three types of file names: simple, compound and relative. A simple or short,
symbolic name identifies the file in the same directory. Simple give the names
of files, users and programmers, but they must take into account the limitations
of OS as a range of characters, as well as the length of the name. Until
relatively recently, these borders were very narrow. Thus, the popular file
system FAT names were limited to the length of the scheme 8.3 (8 characters -
actually the name of 3 - to name extension), and the file system s5, supported
by many versions of OS UNIX, a simple symbolic name can not contain more than 14
characters. However, the user is much easier to work with long names, because
they can give the files easy to remember names, clearly talking about that
contains the file and the atom. Therefore, today's file systems, as well as
improved versions of existing file systems are usually simple symbolic support
long file names. For example, file systems, NTFS and FAT32, members of the
operating system, Windows NT, the file name can contain up to 255 characters.
Examples of simple file names and directories: quest_u1.doc task-entran. exe
annex to the CD 254L in Russian yazyke.doc Installable filesystem manager.doc In
the hierarchical file systems, different files are allowed to have the same
simple character names provided that they belong to different directories. So
here is scheme a lot of files - a simple name: To uniquely identify the file in
such systems is the so-called full name. Full name is a simple chain of symbolic
names of all directories, through which passes the path from the root to the
file. Thus, the full name is a compound in which the simple names separated by
the separator in the OS. Often separated by a forward or backward slash, the
state had not addressed the root directory.
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