The logical organization of the file system
The logical organization of the file system One of the main tasks of the
operating system is to provide users with data stored on discs. For this
operating system replaces the physical structure of stored data a user-friendly
logical model. The logical model of the file system materialized in the form of
a directory tree on the screen tools such as Norton Commander or Windows
Explorer, in the composite character file names, the teams work with files. The
basic element of this model is a file that is the same as the file system as a
whole, can be characterized as a logical or physical structure.
Goals and Objectives of the file system File - it named the area of external
memory, which can record and from which you can read the data. Files are stored
in memory, depending on the power supply on, usually - on magnetic disks.
However, there are no rules, without exception. One such exception is the so-called
electronic disk when memory is created the structure, simulating the file system.
The main purpose of the file listed below. Long-term and safe storage of
information. Sustainability is achieved through the use of storage devices that
are not dependent on nutrition, and high reliability is determined by means of
protecting access to files and the general organization of the code system, in
which the failure of equipment often do not destroy information stored in files.
Sharing of information. The files provide a natural and easy way of separation
of information between applications and users through the simple presence of a
man of character and persistence of stored information and the location of the
file. You must have a convenient means of working with files, including catalogs,
reference books, which combine the files into groups, search the files on the
grounds set of commands to create, modify and delete files. The file can be
created by one user, and then used quite a different user, the creator of the
file or the administrator can define access to other users. These goals are
implemented in the OS file system. File System (FS) - is part of the operating
system, including: all the files on the disk; sets of data structures used to
manage files, such as directories of files, file descriptors, tables and the
distribution of free disk space occupied; a set of system software for
implementing the various operations on files, such as creating, destroying,
reading, writing, calling and searching files. A file system that allows a
program to dispense a set of fairly simple to perform an action on some abstract
object of a file. In doing so programmers do not have to deal with the details
of the actual location of data on disk, buffering the data and other low-level
problems with long-term data storage device. All these functions of the file
system itself. A file system allocates disk memory, support for naming files,
displays the file names to the appropriate address for external memory that
provides access to data, supports the division, protect and restore the files.
Thus, the file system plays the role of the intermediate layer shielding the
complexities of long-term physical storage of data, and creating programs for
more than a simple logic model of the warehouse, as well as providing them with
easy-to-use set of commands for manipulating files. The tasks to be resolved FC,
depending on the method of computing process as a whole. The simplest type - the
FS is in single-and odnoprogrammnyh OS, which include, for example, MS-DOS. The
main function of such FS focus on the following tasks: naming files; programming
interface for applications; mapping the logical model of the file system on the
physical organization of the data warehouse; the sustainability of the file
system to power failures, errors of hardware and software. FC complicated tasks
in multiprogrammnyh single operating system, which, although intended for the
work of one person, but give him the opportunity to run multiple processes. One
of the first operating system of this type was the OS / 2. For the above
objectives are added to the new task of sharing files from multiple processes.
The file in this case is a shared resource, and therefore, the file system must
address the whole range of problems associated with such resources. In
particular, the FS should be provided locks the file and its parts, preventing
the race, the exclusion of blind alleys, the harmonization of copies, etc. In
multi-user systems is another challenge, the protection of files from one user
to access another user. More complex are the functions of the FS, which is
composed of a network operating system. This topic is dealt with in the last
chapter of a book on the management of network resources.
Next part
|
O
wlCom Software
