All subsequent references to the file use this

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Unformatted text preview:, where .c and .z are used to indicate that it is a C language program file that has been compressed using the Ziv-Lempel compression algorithm. In such file names, the second and subsequent parts are called file extensions. File extensions usually indicate something about the file and are often used by applications to check for the intended type of file before operating on it. For example, a C language compiler may actually insist that the files it is to compile end in 4c, and it may refuse to compile them if they do not. Some applications automatically supply their own extensions, such as .doc (for a Microsoft Word file) or .wk4 (for a Lotus 1-2-3 file). Some typical file extensions and their meanings are shown in Figure 14.17. File extension .bas .c .ftn .pas .obj .bin .lib .dat .hip .man .txt .bak .doc .wav .wk4 .xls .jpg .gif Its meaning Basic source program file C source program file Fortran source program file Pascal source program file Object file (compiler output, not yet linked) Executable binary program file Library of .obj files used by the linker Data file Text file for HELP command Online manual page file General text file Backup file Microsoft word document file Microsoft windows sound file Lotus 1-2-3 spreadsheet file Microsoft Excel spreadsheet file JPEG graphics file GIF graphics file Figure 14.17. Some typical file extensions and their meaning. Directories Directories are used by operating systems to map file names to their corresponding file attributes and file data, and also to provide greater flexibility to users in file naming. How directories help in achieving these objectives is briefly explained below. Directory Contents A directory has a number of entries, one per file. As shown in Figure 14.18, each entry contains a file name, the attributes of the file or pointer to the data structure containing the attributes, and pointer to the file data (disk address where the file data is stored). File File attributes or pointer to data Pointer to file...
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This document was uploaded on 04/07/2014.

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