comsie 2101 file mamm

File Management System

File Management System

File Manager is also called the?

Creating, deleting, modifying, controlling access to files

File Manager is also called the File Management System and is the software responsible for:

Files

Are the building blocks of any operation system. Permanent storage of information & data.

File

Represent program and data.

Executable file

The output of program is called?

File access mechanism

Refers to the manner in which the records of a file may be accessed.

• Sequential File Access

• Direct File Access

• Indexed File Access

There are several ways to access files:

Sequential File Access

Is a method of accessing data sequentially/one record at a time by starting from the beginning of the file to its end.

Direct File Access

Also known as Random file access.

Direct File Access

Allows users to access data directly from any location within the file without the need to read/write all the records that come before it.

Indexed File Access

Is a method that incorporates the benefits of both sequential and direct file access.

File type

Refers to the ability of the operating system to distinguish different types of file such as text files, source files, and binary files etc.

Ordinary files

These are the files that contains user information. These may have text, databases or executable program.

Directory files

Contains list of file and other related information to those files.

Directory files

Also known as “folders” in other operating systems. Folders that holds and organize multiple files.

Special Files

These files are also known as device files.

-Character special files

-Block special files

Two types of special files?

Character special files

Data is handled character by character as in case of terminals or printers.

Block special files

Data is handled in blocks as in the case of disks and tapes.

Create, Delete, Open, Close, Read, Write, Append, Seek, Rename

File operations

Write

This file operation is used to write the data to the file, again, generally at the current position.

Append

This file operation is same as the file write operation except that the file append operation only add the data at the end of the file.

Seek

For random access files, a method is needed just to specify from where to take the data.

Directory

Is a list of files that stores all the related information about the file it hold with the contents. _________is a list of files.

Single-level directory structure

All the files are placed in one directory

Single-level directory structure

Two-level directory structure

The system maintains a master block that has one entry for each user.

Two-level directory structure

Tree-structured directory structure

The directory themselves are files. This files to the possibility of having sub-directories that can contain files and sub-subdirectories

Tree-structured directory structure

Layered File System

There are 6 layers

Layered File System

Application Program Layer

user creates application program

Logical File System Layer

manages the meta data information

File Organization Module Layer

maintain information about file

Basic File System Layer

-generate command for device driver

-also manage buffer memory and cache

I/O Control Interface Layer

it consists of device driver & interrupt handler. transfer data: between main memory to disk system.

Physical Hardware Device Layer

contain actual hardware device

Data compression

A reduction in the amount of bits required to represent data is known as?

program, formula, algorithm

Compression is performed by a ______ that uses a ________ or _______ to determine how to shrink the size of the data.