The logical organization of the file system
two files have a simple name mam exe, but their names composite / depart / main.exe
and / user / anna / main.exe different. In the tree-file system of file and its
full name is available each one correspondence single file - a full name. In the
file system of networking, the file can be included in several directories, and
thus have more than one full names, this is true with one file - a lot of proper
names. In both cases, the file is uniquely identified by full name. The file can
be identified as a relative name. Relative file name is determined by the notion
of current directory. For each user at a time, one of the directory file system
is ongoing, and this directory is selected by the user on command OS. File
system captures the name of the current directory, then use it as a complement
to the relative name for the education of full file name. If you use relative
file names the user identifies a chain of names of directories, which passes
through the route from the current directory to the file. For example, if the
current directory is a directory / user, then the relative file name / user /
anna / main.exe as follows: anna / main.exe. Some operating systems are allowed
to assign the same few simple file names, which can be interpreted as an alias.
In this case, as in the system with the network structure, a line single file -
a lot of proper names, because everyone simply the file name corresponds to at
least one full name. And although the full name uniquely identifies the file,
the operating system easier to work with the file if the files and their names
have a mutually-one correspondence. To this end, it assigns a unique file name,
so that the true relationship single file - a unique name. The unique name there,
along with one or more character names assigned to files by users or
applications. The unique name is a numeric identifier, and is intended only for
the operating system. An example of such a unique file name is the inode number
in UNIX. Mounting In general, the computer system may have multiple disk devices.
Even a typical personal computer is usually a hard disk drive, a drive for
floppy disks and storage for CD-ROM drive. Powerful computers are also typically
equipped with a large number of disk drives, the drives are installed packages.
Moreover, even a physical device through the operating system can be presented
in several logical devices, in particular by partitioning space into sections.
The question is how to organize files in a storage system with multiple external
memory? The first solution is that in each of the devices available offline file
system, that is, the files are on the device, described by the directory tree,
not related to the directory trees on other devices. In this case for clear
identification of the user files, along with a composite character file name to
indicate a logical device identifier. An example of such an autonomous existence
of the file systems is the operating system MS-DOS, which includes the full name
of the file identifier of a logical drive letter. So, when you access files on a
disk, the user must specify the name of the disk: A: \ privat \ letter \ uni \
let1 doc [1]. Another option is to store files such an organization in which the
user is given the opportunity to combine file systems located on different
devices into a single file system, described by a single directory tree. This
operation is called mounting Consider how the operation is carried out by the
example of operating system UNIX. Among all available in the logical disk
devices, the operating system allocates one device, called the system. Suppose
there are two file systems located on different logical drives, one of the disks
is a system. File system, based on the system drive, appointed by the root. For
communication hierarchies of files in the root file system selects some of the
existing directory, in this example - a directory man. Upon completion of the
selected directory mountpoints man becomes the root of the second file system.
Through this directory assembled a file system is connected both to the general
tree podderevo After mount a common file system for the user no logical
distinction between the root and mounted file systems, in particular the naming
of files produced in the same manner as if it had been from the beginning was a
single.
Next part
|
O
wlCom Software
