comp229-slide-7 - Concordia university Department of...

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Lesson 7 - File management 1 Concordia university Department of computer science System software – COMP229 Lesson 7 : File management © Author : Kerly Titus
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Lesson 7 - File management 2 File management Contents 1. Principles 3 2. File structures 12 3. Disk block management 18 4. Directories 28 5. Unix 36 6. Key points 69 7. References 73
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Lesson 7 - File management 3 1. Principles Introduction File structures File access methods File operations File attributes
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Lesson 7 - File management 4 Principles Introduction Definition. – A file represents a logical structure that abstracts the characteristics of a peripheral device. – A file is used to store a collection of related data permanently on a storage device. – A file data may represent a sequence of bits, bytes, records, etc. File types. – Program files (source, object, executable). – Static and dynamic library files. – Data files. – Text files. – Multimedia files (audio, video, image). – Archive file. – Script file.
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Lesson 7 - File management 5 Principles Introduction 0 n-1 Physical block Files (data + descriptor) Device driver •Disk • Buffer • Program open(…); read(…); write(…); close(…); Logical block • File management organization Open file Directories File system File pointer
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Lesson 7 - File management 6 Principles Introduction File management organization. – File system. A structure that is used to map and to manage the files on a storage device. – Physical block. Smallest storage units on a disk device. – Descriptor. Structure that describes the attributes of a file. – Directory. Organizational structure that holds the files on a storage device. – Logical block. Content of a physical block that is stored in a file buffer. – Buffer. Temporary memory area that stores the physical blocks that are currently being accessed. – File pointer. Stores the current access position in a file. –D e v i c e d r i v e r . System program that controls the transfer of information between a peripheral device and a program.
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Lesson 7 - File management 7 Principles Introduction Functions of the file manager. – To provide a user-friendly interface to applications that access a peripheral device. – To map the physical and logical blocks of a file. – To maintain the integrity and the consistency of the information that is stored on files. – To detect and correct errors during file transfer operations. – To optimize the system performance during file access operations. – To allow file sharing among competing users or applications. – To protect files against unauthorized accesses. – To provide a directory structure to organize and to search files on a storage device.
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This note was uploaded on 03/25/2010 for the course COMP COMP229 So taught by Professor Guy during the Spring '10 term at Concordia Canada.

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comp229-slide-7 - Concordia university Department of...

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