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9 Cards in this Set
- Front
- Back
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What are some file operations (6)? |
Create - allocates space, creates new entry in directory write - Sys call specifying name of file and info to be written read - Specify name of file and where to put in memory. Read pointer to location in file where next read will happen is required. Usually kept as a current-file-position pointer for both read and write. Reposition within - Moves current file position pointer (File seek) delete - Search directory for named file, release all file space, erase directory entry truncate - Set file length to 0 and free file space, but keep attributes |
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What is sequential file access? |
Reading information in a file, one record after another. |
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What is direct file access? |
Direct access (relative access), is where a file is made up of fixed-length logical records that allow programs to read and write records in no particular order. Typically use relative block numbers, with 0 being first block for file, but might be address 14703 on disk. |
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What is single-Level directory? |
All files are contained in the same directory. Must have unique names. |
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What is two-level directory? |
Each user has their own user file directory. This is stored in a master file directory. When a user wants a file, their oown UFD is searched. So file names do not have to be unique to all users, only to the current user. |
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What is tree-structured? |
Two-level extended to a tree. Each process has a current directory of files that are current interest to the process. |
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What is acyclic graph directories? |
Allows shared directory between two users, creates a link (pointer) to another file or subdirectory. Link is resolved to locate file. |
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What are general graph directories? |
Yeah...No idea |
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Consistency semantics in unix vs session? |
Unix: Writes to an open file by a user are immediately visible to other users who have the file open Pointer changes by one user affect all users Session: Writes to an open file are not immediately visible Once file is closed, changes are only visible in later sessions. Already open instances of a file do not show changes. |
