🗊Презентация File systems and directories. (Chapter 11)

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Слайды и текст этой презентации


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Chapter 11
File Systems and Directories
Описание слайда:
Chapter 11 File Systems and Directories

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Chapter Goals
Describe the purpose of files, file systems, and directories
Distinguish between text and binary files
Identify various file types by their extensions
Explain how file types improve file usage
Define the basic operations on a file
Описание слайда:
Chapter Goals Describe the purpose of files, file systems, and directories Distinguish between text and binary files Identify various file types by their extensions Explain how file types improve file usage Define the basic operations on a file

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Chapter Goals
Compare and contrast sequential and direct file access
Discuss the issues related to file protection
Describe a directory tree
Create absolute and relative paths for a directory tree
Describe several disk-scheduling algorithms
Описание слайда:
Chapter Goals Compare and contrast sequential and direct file access Discuss the issues related to file protection Describe a directory tree Create absolute and relative paths for a directory tree Describe several disk-scheduling algorithms

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File Systems
File   A named collection of related data
File system   The logical view that an operating system provides so that users can manage information as a collection of files
Directory  A named group of files
Описание слайда:
File Systems File A named collection of related data File system The logical view that an operating system provides so that users can manage information as a collection of files Directory A named group of files

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Text and Binary Files
Text file   A file in which the bytes of data are organized as characters from the ASCII or Unicode character sets
Binary file  A file that contains data in a specific format, requiring interpretation
Описание слайда:
Text and Binary Files Text file A file in which the bytes of data are organized as characters from the ASCII or Unicode character sets Binary file A file that contains data in a specific format, requiring interpretation

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Text and Binary Files
The terms text file and binary file are somewhat misleading
They seem to imply that the information in a text file is not stored as binary data
Ultimately, all information on a computer is stored as binary digits 
These terms refer to how those bits are formatted: as chunks of 8 or 16 bits, interpreted as characters, or in some other special format
Описание слайда:
Text and Binary Files The terms text file and binary file are somewhat misleading They seem to imply that the information in a text file is not stored as binary data Ultimately, all information on a computer is stored as binary digits These terms refer to how those bits are formatted: as chunks of 8 or 16 bits, interpreted as characters, or in some other special format

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File Types
Most files, whether they are in text or binary format, contain a specific type of information
	For example, a file may contain a Java program, a JPEG image, or an MP3 audio clip
The kind of information contained in a document is called the file type
	Most operating systems recognize a list of specific file types
Описание слайда:
File Types Most files, whether they are in text or binary format, contain a specific type of information For example, a file may contain a Java program, a JPEG image, or an MP3 audio clip The kind of information contained in a document is called the file type Most operating systems recognize a list of specific file types

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File Types
File names are often separated, usually by a period, into two parts
Main name
File extension
The file extension indicates the type of the file
Описание слайда:
File Types File names are often separated, usually by a period, into two parts Main name File extension The file extension indicates the type of the file

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File Operations
Create a file
Delete a file
Open a file
Close a file
Read data from a file
Write data to a file
Reposition the current file pointer in a file
Описание слайда:
File Operations Create a file Delete a file Open a file Close a file Read data from a file Write data to a file Reposition the current file pointer in a file

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File Access
Sequential access  Information in the file is processed in order, and read and write operations move the current file pointer as far as needed to read or write the data
	The most common file access technique, and the simplest to implement
Описание слайда:
File Access Sequential access Information in the file is processed in order, and read and write operations move the current file pointer as far as needed to read or write the data The most common file access technique, and the simplest to implement

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File Access
Описание слайда:
File Access

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File Access
Direct access  Files are conceptually divided into numbered logical records and each logical record can be accessed directly by number
Описание слайда:
File Access Direct access Files are conceptually divided into numbered logical records and each logical record can be accessed directly by number

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File Access
Описание слайда:
File Access

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File Protection
In multiuser systems, file protection is of primary importance
We don’t want one user to be able to access another user’s files unless the access is specifically allowed
A file protection mechanism determines who can use a file and for what general purpose
Описание слайда:
File Protection In multiuser systems, file protection is of primary importance We don’t want one user to be able to access another user’s files unless the access is specifically allowed A file protection mechanism determines who can use a file and for what general purpose

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File Protection
A file’s protection settings in the Unix operating system is divided into three categories
Owner
Group
World
Описание слайда:
File Protection A file’s protection settings in the Unix operating system is divided into three categories Owner Group World

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Directory Trees
A directory of files can be contained within another directory
	The directory containing another is usually called the parent directory, and the one inside is called a subdirectory
Directory tree   A logical view of a file system; a structure showing the nested directory organization of a file system
Root directory  The directory at the highest level
Описание слайда:
Directory Trees A directory of files can be contained within another directory The directory containing another is usually called the parent directory, and the one inside is called a subdirectory Directory tree A logical view of a file system; a structure showing the nested directory organization of a file system Root directory The directory at the highest level

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Directory Trees
Описание слайда:
Directory Trees

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Directory Trees
At any point in time, you can be thought of as working in a particular location (that is, a particular subdirectory)
Working directory  The subdirectory in which you are working
Описание слайда:
Directory Trees At any point in time, you can be thought of as working in a particular location (that is, a particular subdirectory) Working directory The subdirectory in which you are working

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A Unix Directory Tree
Описание слайда:
A Unix Directory Tree

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Path Names
Path  A text designation of the location of a file or subdirectory in a file system, consisting of the series of directories through which you must go to find the file
Absolute path  A path that begins at the root and specifies each step down the tree until it reaches the desired file or directory
Relative path   A path name that begins at the current working directory
Описание слайда:
Path Names Path A text designation of the location of a file or subdirectory in a file system, consisting of the series of directories through which you must go to find the file Absolute path A path that begins at the root and specifies each step down the tree until it reaches the desired file or directory Relative path A path name that begins at the current working directory

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Path Names
Examples of absolute path
C:\Program Files\MS Office\WinWord.exe
C:\My Documents\letters\applications\vaTech.doc
C:\Windows\System\QuickTime
Suppose the current working directory is
C:\My Documents\letters
Then the following relative path names could be used
cancelMag.doc
applications\calState.doc
Описание слайда:
Path Names Examples of absolute path C:\Program Files\MS Office\WinWord.exe C:\My Documents\letters\applications\vaTech.doc C:\Windows\System\QuickTime Suppose the current working directory is C:\My Documents\letters Then the following relative path names could be used cancelMag.doc applications\calState.doc

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Disk Scheduling
File systems must be accessed in an efficient manner
As a computer deals with multiple processes over a period of time, a list of requests to access the disk builds up
Disk scheduling  The technique that the operating system uses to determine which requests to satisfy first
Описание слайда:
Disk Scheduling File systems must be accessed in an efficient manner As a computer deals with multiple processes over a period of time, a list of requests to access the disk builds up Disk scheduling The technique that the operating system uses to determine which requests to satisfy first

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Disk Scheduling
Описание слайда:
Disk Scheduling

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Disk Scheduling
First-Come, First-Served   Requests are serviced in the order they arrive, without regard to the current position of the heads
Shortest-seek-time-first (SSTF)  Disk heads are moved the minimum amount possible to satisfy a pending request
Scan   Disk heads continuously move in and out servicing requests as they are encountered
Описание слайда:
Disk Scheduling First-Come, First-Served Requests are serviced in the order they arrive, without regard to the current position of the heads Shortest-seek-time-first (SSTF) Disk heads are moved the minimum amount possible to satisfy a pending request Scan Disk heads continuously move in and out servicing requests as they are encountered

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Disk Scheduling
SCAN Disk Scheduling works like an elevator
An elevator is designed to visit floors that have people waiting. In general, an elevator moves from one extreme to the other (say, the top of the building to the bottom), servicing requests as appropriate.
The SCAN disk-scheduling algorithm works in a similar way, except instead of moving up and down, the read/write heads move in toward the spindle, then out toward the platter edge, then back toward the spindle, and so forth.
Описание слайда:
Disk Scheduling SCAN Disk Scheduling works like an elevator An elevator is designed to visit floors that have people waiting. In general, an elevator moves from one extreme to the other (say, the top of the building to the bottom), servicing requests as appropriate. The SCAN disk-scheduling algorithm works in a similar way, except instead of moving up and down, the read/write heads move in toward the spindle, then out toward the platter edge, then back toward the spindle, and so forth.

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How To Transfer Files
FTP Clients
FileZilla is one of the best
Описание слайда:
How To Transfer Files FTP Clients FileZilla is one of the best

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Other Types Of File Transfers
& Systems
Secure FTP (SSH, SFTP, FTPS)
Network File System (NFS)
Storage Area Networking (SANs)
RAID Devices
Peer-to-Peer (P2P)
BitTorrent
Описание слайда:
Other Types Of File Transfers & Systems Secure FTP (SSH, SFTP, FTPS) Network File System (NFS) Storage Area Networking (SANs) RAID Devices Peer-to-Peer (P2P) BitTorrent

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BitTorrent
Описание слайда:
BitTorrent

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Have A Nice Night
Описание слайда:
Have A Nice Night



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