Organization of the file system
carried out with the so-called current position, which is the offset from the
beginning of the file. Knowing the size of the block, it is easy to calculate
the number of cluster containing the current position. Address same block
desired disk can then be drawn from the index file. The basic operation is
carried out in relation to the file is read from the drive unit and relocate it
in the buffer, located in the main memory.
File system enables via directories (folders, directories), a unique file name
linked with the secondary memory blocks containing data file. Hierarchical
directory structure used to manage files, is another example of the index
structure. In this case, directories or folders role indices, each of which
contains a reference to its subdirectories. From this perspective, the entire
file system is a large computer file indexed.
The term "file system" include: ? totality of all files on disk, ? sets of data
structures used to manage files, such as directories of files, file descriptors,
tables and the distribution of free space on a disk employee, ? set of system
software which implements the file management, in particular: the creation,
destruction, reading, writing, naming, search and other operations to the files.
Files managed OS. The way they are structured, named used, protected, realized
one of the main topics of OS design.
List the main functions of the file system: 1. Identification files. Tying the
filename with the space allotted to it external memory. 2. The distribution of
files between the external memory. To work with a specific file is not necessary
to have information on the location of the file on the external medium. For
instance, to download the document in the editor from the hard drive, we do not
need to know on what side of what the magnetic disk, and what the cylinder in
which sector is required document. 3. Ensuring reliability and fault tolerance.
The value of information can greatly exceed the cost of a computer. 4. The
protection of NSD. 5. Ensuring access to a file-sharing without requiring the
user to special efforts to ensure the synchronization of access. 6. Ensuring
high productivity. Sometimes saying that the file-named set of related
information recorded in secondary memory. For most users, the file system is the
most visible part of the OS. It provides a mechanism for online storage and
access of data, and OS program for all users of the system. In terms of file-user
minimum external memory, the data that is recorded on the disc must be composed
of some files.
An important aspect of the organization of the file system-cost accounting
operations interaction with the secondary memory. The process of readers drive
unit consists of a positioning reader over the head track containing the