CHAPTER 10:FILE-SYSTEM INTERFACE
CHAPTER 10: FILE-SYSTEM INTERFACE
CHAPTER 10:FILE-SYSTEM INTERFACE o File Concept o Access Methods o Directory Structure o File-System Mounting o File Sharing o Protection
CHAPTER 10: FILE-SYSTEM INTERFACE File Concept Access Methods Directory Structure File-System Mounting File Sharing Protection
OBJECTIVES o To explain the function of file systems o To describe the interfaces to file systems o To discuss file-system design tradeoffs, including access methods,file sharing,file locking,and directory structures o To explore file-system protection
OBJECTIVES To explain the function of file systems To describe the interfaces to file systems To discuss file-system design tradeoffs, including access methods, file sharing, file locking, and directory structures To explore file-system protection
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DISK
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Symbolic Open Levels of file name file ID abstraction USER File system interface Files/ directories Directory High-level file and FS management directory functions Logcal block# Basic file system Open/close functions Physical device address Device organization Low-level data methods access functions 1O system interface Logical block# 6
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FILE CONCEPT o Contiguous logical address space o Types: ·Data o numeric o character o binary ·Program
FILE CONCEPT Contiguous logical address space Types: Data numeric character binary Program
FILE STRUCTURE o None-sequence of words,bytes o Simple record structure 。Lines 。Fixed length ·Variable length o Complex Structures ·Formatted document Relocatable load file o Can simulate last two with first method by inserting appropriate control characters o Who decides: ·Operating system Program
FILE STRUCTURE None - sequence of words, bytes Simple record structure Lines Fixed length Variable length Complex Structures Formatted document Relocatable load file Can simulate last two with first method by inserting appropriate control characters Who decides: Operating system Program
FILE ATTRIBUTES o Name-only information kept in human-readable form o Identifier-unique tag(number)identifies file within file system o Type-needed for systems that support different types o Location-pointer to file location on device o Size-current file size o Protection-controls who can do reading,writing, executing o Time,date,and user identification-data for protection,security,and usage monitoring o Information about files are kept in the directory structure, which is maintained on the disk
FILE ATTRIBUTES Name – only information kept in human-readable form Identifier – unique tag (number) identifies file within file system Type – needed for systems that support different types Location – pointer to file location on device Size – current file size Protection – controls who can do reading, writing, executing Time, date, and user identification – data for protection, security, and usage monitoring Information about files are kept in the directory structure, which is maintained on the disk
FILE OPERATIONS o File is an abstract data type o Create o Write o Read o Reposition within file o Delete o Truncate o Open(F:)-search the directory structure on disk for entry F;,and move the content of entry to memory o Close (F)-move the content of entry F;in memory to directory structure on disk
FILE OPERATIONS File is an abstract data type Create Write Read Reposition within file Delete Truncate Open(Fi ) – search the directory structure on disk for entry Fi , and move the content of entry to memory Close (Fi ) – move the content of entry Fi in memory to directory structure on disk