The document discusses file management and operations. It describes how files are organized through creating, storing, removing, opening, and closing files. It also covers file attributes like name, type, location, size, date/time of creation and modification, and protection. Common file operations are also summarized such as creating, writing, reading, repositioning, deleting, truncating, and appending files. The document also discusses file types and how operating systems can recognize and support different file extensions.

1. File Management
Organization of data
- Creating a file
- Storing a file in required directory
- Removing a file
- Opening a file
- Closing a file
- Maintaining of file details
- Name, Type, location, size ,
date and time of creation or modification
- File Protection
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2. File Attributes
- Name
- Type
- Location
- Size
- Protection
- Time, Date and User Identification
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3. File Attributes
Name
- Given by the user
- Only information that is kept in human readable form
Type
- Information required by systems that support different
types
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4. File attributes
Location
- A pointer to a device and to the
location of the file on that device
Size
- Current size of file (in bytes or words )
- Max size allowed
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5. File Attributes
Protection
- Access control information
( read, write and execute privileges )
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6. File Attributes
Time, date and user identification
- Creation
- Last modification
- Last use
(Useful for protection, security and usage monitoring )
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7. Basic File Operations ( Minimal Set )
1. Creating a file
2. Repositioning within a file
3. Deleting a file
4. Truncating a file
5. Reading a file
6. Writing a file
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8. Basic File Operations
1. Creating a file
• Allocation of space for the file in the file system
• Making an entry for the new file in the directory
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9. Basic File Operations
2. Writing a file
• Use a system call specifying
- Name of the file
- Information to be written
• Search directory for the associated entry
• Keep a write pointer
• Update write pointer after every write
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10. Basic File Operations
3. Reading a file
• Use a system call specifying
- Name of the file
- Address where to put the contents read
• Search directory for the associated entry
• Keep a read pointer
• Update read pointer after every read
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11. Basic File Operations
4. Repositioning within a file
• Also known as file seek operation
• Search directory for the appropriate entry
• Set current-file-position to a given value
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12. Basic File Operations
5.Deleting a file
• Search the directory for the named file
• Release all file space
• Erase the directory entry
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13. Basic File Operations
6. Truncating a file
• File contents erased
• Name and attributes of file unchanged
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14. Other File Operations
• Appending
• Renaming
Appending
Add some information at the end of the file
Renaming
Name of file changed
All other attributes unchanged
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15. Basic file operations can be combined to implement other
operations
Ex : Creating a copy of a file
- Create a new file
- Read from old file
- Write to new file
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16. Other Desirable Operations
Allow the user to get and set the various attributes of a file
Ex : i) get the file length
ii) set file attributes like file’s owner
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17. Other Desirable Operations
Most file operations involve searching the directory for the
entry associated with the named file
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18. To Avoid Constant Searching
• Many systems open a file when file first is used
• The operating system keeps a small table called the
Open file table
• Open file table contains information about open files
• When a file operation is requested, an index into the
open file table is used
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19. Other File Operations
When a file is no longer actively used, it is closed by
the process and the O.S. removes its entry in the Open
file table
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20. Other File Operations
• Some systems implicitly open a file when it is first referenced
• Close it automatically when the program that opened the file
terminates
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21. Other File Operations
Most systems require that a file be opened explicitly by the
programmer with a system call ( open ) before that file can be
used
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22. File Type Usual extension Function
Executable Exe, com, bin or none Ready to run machine
language program
Object obj, o Compiled, machine language,
not linked
Source code c, p, pas, f77, asm, a Source code in various
languages
Batch bat, sh Commands to the command
interpreter
Text txt, doc textual data,documents
Word Wp, tex, rrf etc Various word processor
Processor formats
Library Lib, a Libraries of routines
Print or view ps, dvi, gif ASCII or binary file in a
format for printing or viewing
Archive arc, zip, tar Related group of files for
archiving or storage
Fig : Common File Types
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23. File Type
One major consideration in designing a file system, and the
entire operating system, is whether the operating system
should recognize and support file types
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24. File Type
• If the operating system recognizes the type of a file
• it can then operate on the file in reasonable ways
• Ex : An attempt to print a binary-object form of a
program file can be prevented
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25. File Type
To implement file types, include the type as part of
the file name
For Ex : letters , documents
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26. File Type
The file name is split into two parts
- a name
- an extension
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27. File Type
• The file name is usually separated from the
extension by a period ( dot ) character
Ex : paycalc. cpp
• The name can consists up to 8 characters followed
by a period
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28. File Type
The extension tells what the file type is
• Extension can be up to 3 characters
• System uses the extension to indicate the type of the
file
• Type of operations that can be done on that file
For ex : .com , .exe & .bat extension are executable
file
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29. Summary
In this class, you have learnt
- file concept
- Understand file operations
- Know various file types
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