The document outlines the key components and functions of a file system and input-output control system (IOCS), detailing how files are managed, accessed, and protected. It explains different file organizations such as sequential, direct, and index sequential, as well as the structure and operations related to directories. Additionally, it discusses the use of hash tables and B+ trees for efficient directory organization and searching.

1. Presented By:
Apoorva Nagar
MCA/25013/18

2. FILE SYSTEM
 Computer user stores program and data in file so that
they can be used conveniently and preserved across
computing session.
 Operating system organise the file management into two
components: File system
Input-output control system(IOCS)
File Processing
 This term is used to describe the general sequence of
opening the file,reading the file or writing in file and
closing of file.
 File system locate the file using directory structure
which is the arrangement of many directories.

3. File system
 A file system views the file as a collection of data
that is owned by the user and can be shared with
authorised users.
 File system provides protection of files from illegal
access.
 It provides directory structure for convenient
grouping of files.
 It provides file sharing semantics for concurrent
accesses to a file.
 It provides reliable storage of file.

4. Input-Output Control System
 The IOCS views a file as a repository of data that
need to be accessed speedily and are stored in a I/O
device that need to be used efficiently.
 IOCS policies ensures efficient operation of I/O
devices and efficient file processing through
mechanism modules.
 These mechanism modules in turn invoke kernel
through system calls.
 It provides efficient access to data in a file.

5. FILES AND FILE OPERSTIONS
 A file system houses and organises different types of
files like data files,executable programs, video clips,
photos etc.
 These file types are grouped into two classes:
Structured files
Byte stream files
 A structured file is a collection of records which are
collection of fields which contains a single data
item.
 Byte stream file is “flat” that is there are no records
and fields in it.

6. OPERATIONS ON FILES

7. FUNDAMENTAL FILE ORGANISATIONS
File organisation is a combination of two features- method
of arranging records in the file and a procedure to access
them.
Sequential File Organisation
 In this records are stored in an ascending or descending
sequence according to the key field.
 It supports two kind of action-read the next record and
skip the next record.
Direct File Organisation
 It provides convenience and efficiency of file processing
when records are accessed in random order.
 Records are accessed through direct-access files where
in read/write command needs to mention value in key
field

8. Index Sequential File Organisation
 An index helps to determine the location of a record
from its key value.
 Index of a file contains an index entry with the
format
(key value, disk address) for each key value in
file.
 Index Sequential File Organisation is a hybrid
organisation that combines elements of the indexed
and the sequential file organisation.

9. DIRECTORIES
 A directory contains the information about a group of
files.
 Fields in Directory Entry:

10. Directory Tree
 Most file system contains the feature that allow the
user to create new directory,give it a name of user
choice and create other directories and files in it
upto user desired level. The resulting directory
structure is called directory tree.
 File system provides a directory called root that
contains the home directory of each user.
Operations On Directories
 Searching
 Maintenance operations like creating/deleting
files,updating file entries, listing file entries,
deleting directories.

11. ORGANISATION OF DIRECTORIES
When directories contains large number of entries Hash
tables and B+ tree are used.
Hash Table Directory
 A directory can be maintained using hash table
organisation Hash with opening address.
 When new files are created hash function h is applied
which yield entry number e.
 To find unused entry, entries given by (e+1)mod(n) is
checked repeatedly. n is size of hash table
B+ Directory
 In a B+ directory information about files are recorded
only in leaf node of the tree.
 Non leaf nodes contains index entries and are used
merely to direct the search to appropriate part of the
tree.
 It has the capability of fast search.