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FILE SYSTEM STORAGE
1 File Concept
ü A file is a named collection of related information that is recorded on secondary storage.
ü 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.
Examples of files:
A text file is a sequence of characters organized into lines (and possibly pages).
A source file is a sequence of subroutines and functions, each of which is further organized as declarations followed by executable statements. An object file is a sequence of bytes organized into blocks understandable by the system’s linker. An executable file is a series of code sections that the loader can bring into memory and execute.
2 File Attributes
Name: The symbolic file name is the only information kept in human readable form.
Identifier: This unique tag, usually a number identifies the file within the file system. It is the non-human readable name for the file.
Type: This information is needed for those systems that support different types.
Location: This information is a pointer to a device and to the location of the file on that device.
Size: The current size of the file (in bytes, words or blocks)and possibly the maximum allowed size are included in this attribute.
Protection: Access-control information determines who can do reading, writing, executing and so on.
Time, date and user identification: This information may be kept for creation, last modification and last use. These data can be useful for protection, security and usage monitoring.
3 File Operations
v Creating a file
v Reading a file
v Repositioning within a file
v Deleting a file
v Truncating a file
4 File Types
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