- Facts:
- Data is
stored in (data) files
- A file consists of a number of (disk) blocks
- Data is
stored in (data) files
- Block:
- Block =
a logical group
(created by software)
of sectors:
Sector of a disk Disk block 
A section contains about 512 bytes and it is too small for one disk operation
A block is usually 8 Kbytes
Important fact:
- One disk (read/write) operation
will always
access one disk block
I.e.: block is the (logical) unit of read/write performed used by the Operating System
- Block =
a logical group
(created by software)
of sectors:
- File:
- File = a
(logical) unit
used to
store data
- A file
consists a
list of (data) blocks
- The list of (data) block of
a file is
stored in
a directory entry
The format of a directory entry contains:
block numbers <-------------------> +-----------+-------------------+-+-+-+-+-+ ...... +-+ | Filename | owner/access info | | | | | | | | +-----------+-------------------+-+-+-+-+-+ ...... +-+
- The directory entries are
stored in the
directory on the
disk
- File = a
(logical) unit
used to
store data
- Directory:
- The directory is
stored in
a number of
special reserved
blocks/tracks
called:
- directory blocks/tracks
- directory blocks/tracks
- The directory is
stored in
a number of
special reserved
blocks/tracks
called:
- Steps to
access the data
stored in a file:
- Use filename to
find the
directory entry of the
file:
- Directory entry
info:
+-----------+-------------------+--+--+-+-+-+ ...... +-+ | Filename | owner/access info |b1|b2| | | | | | +-----------+-------------------+--+--+-+-+-+ ...... +-+
Use the list of block numbers to access the disk blocks of the file
- Use filename to
find the
directory entry of the
file: