os11 - Modified from Lecture Slides for Operating System...

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Operating Systems : File System Interface (Chapter 11) Sung-Yong Park, Ph.D. Department of Computer Science Sogang University Modified from Lecture Slides for Operating System Concepts (6 th Edition) by Silberschatz et. al. Page 2 File System Framework Device Driver File Storage Service File Storage Service Directory Service Directory API Directory API File Operations API File Operations API File System Interface File System Implementation User Kernel System Call Interface System Call Interface Text name File id Hard Disk Hard Disk Floppy Disk CD CD -ROM ROM
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Page 3 File Concept ± OS provides a uniform logical view ( file ) of various information storage devices by abstracting from the physical properties of storage devices. ± A file is a collection of related information that is recorded on secondary storage. ± From a user s perspective, a file is the smallest allotment of logical secondary storage; that is, data cannot be written to secondary storage unless they are within a file. ± Types of file ± Data ± Numeric, alphanumeric, or binary ± Program Page 4 File Structure ± None - sequence of words, bytes such as text file. ± Simple record structure ± Lines ± Fixed length record ± Variable length record ± Complex Structures ± Formatted document (e.g., html) ± Relocatable load file (e.g., object file) ± Can simulate last two with first method by inserting appropriate control characters.
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Page 5 File Attributes ± A file has several attributes: (vary from one OS to another) ± Name – only information kept in human-readable form. ± 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
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os11 - Modified from Lecture Slides for Operating System...

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