1. Definition
• A directory is a file which contains information
about other files in the system
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2. Contents of a Directory Entry
Directory Information about each file
Entry1 File name
File type
Entry2 File size
Owner
Entry3 Protection information
Usage count
Creation time
Entry4
Time of last modification
List of disk blocks used
Fig : A directory having an entry for each file
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3. File System Organization
• File systems on a computer system need organization
• Organization done in two parts
1. Partition file system
2. Create directory
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4. Minidisks and Volumes
Partitions are known as
• Minidisks in IBM world
• Volumes in PC and Macinthosh arenas
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5. File System Organization
1. Partition file system
• Each disk on a system contains at least one partition
• A partition is a low level structure
• Each partition contains files and directories
• A single disk can have multiple partitions
• Each partition is treated as a separate storage device
i..e. each partition is a virtual disk
• Some systems group different physical disks into a single
partition
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6. File System Organization
2. Create directory
• Each partition contains a directory
• A directory is also known as a device directory or volume
table of contents ( VTOC )
• The directory records information about all files on that
partition
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7. File System Organization
directory
Partition A
files
directory Disk 1
Partition B files
Fig : File system organization – Single disk – Multiple partitions
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8. File System Organization
Directory
Disk 2
Partition C Files
Disk 3
Fig : File System organization – Single Partition – Multiple Disks
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9. Quiz
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10. 1. In sequential access method
a) Records are accessed randomly
b) Every alternate record is accessed
c) Records are accessed one after the other
d) None of the above
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11. 2. Direct access is suitable for
a) Payroll application
b) Compilation of a source program file
c) Airline reservation
d) All of the above
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12. 3. An index file
a) Increases speed of accessing data
b) Decreases speed of accessing data
c) Occupies space in addition to data file
d) Both a & c
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13. 4. The access method to be used for processing student
results
a) Direct access
b) Indexed access
c) Sequential Access
d) None of the above
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14. 5. A directory is
a) A file
b) A storage device
c) A system program
d) None of the above
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15. 6. Each entry in a directory stores information such as
a) Name of the file
b) Size of the file
c) Location of the file
d) All of the above
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16. 7. Which of the following is not a directory operation
a) Deleting a file
b) Creating a file
c) Rename a file
d) None
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17. 8. The most common backup device is
a) Keyboard
b) Printer
c) Magnetic tape
d) All of the above
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