This document discusses disk structure, including file allocation and the file directory. It explains that the file allocation table tracks file locations, and that the file directory stores files in a hierarchical structure like folders on a tree. It describes the components of a file directory entry, including the filename, file attributes, and other metadata.

1. Disk Structure
1) File Allocation
2) The file directory

2. Hello!We will see
× what is disk?
× File allocation
× File directory

3. What is
“A disk refers to magnetic media, such as a
floppy disk, the disk in your computer's
hard drive, an external hard drive”

4. 1.File
Allocation
Let’s start with the 1st Topic.

5. ×To keep track of the data stored on disk ,DOS uses a
directory structure .
×The directory structure is the organization of files into a
hierarchy of folders. Computers have used the folder as a
way to help users keep track of where something can be
found.
×The 1st track and sector of a disk contain information about
the disk file structure.

6. Floppy disk
sturcture
Figure

7. Surface Track Sector Information
0 0 1 Boot record
0 0 2-5 File Allocation table
0 0 6-9 File directory
1 0 1-3 File directory
1 0 4-9 Data

8. ×Boot record: Used in startup
×File Allocation Table : A table that the operating system uses to
locate files on a disk.
×File directory: A directory is a location for storing files on your
computer
×Data : File stored by user.

9. The File directory
2nd Topic.

10. A file directory is a location for storing files on your
computer. Directories are found in a hierarchical file
system, such as Linux, MS-DOS, OS/2, and Unix.

11. The directory organized
as a tree, with main
directory (root directory)
as root and the
subdirectories as branch.

12. File directory
Organization
Figure 1.

13. File directory
Organization
Figure 2.

14. Byte Function
0-7 File name (0 is also used as status byte and means
entry has never been used ,5Eh mean file deleted)
and information about file.
8-10 File extension
11 Attribute byte
12-21 Reserved by DOS
24-25 Creation: Hour,Month,Day
26-27 Starting cluster number
28-31 File size in byte
DOS creates a 32-byte directory entry for each file. The format of an entry is as follows :

15. × There are seven sectors in directory
area each with 512 bytes.
× Each file contain 32 bytes,
so there is room for
7x512/32 =112 entries.
× The file entries also may be contained in
subdirectories.

16. × Byte 11 is the attribute byte.
× Each bit specifies a file attribute.
× The attribute byte is created
When file is created.
× It can change also.
× When file is created by default
It has attribute 20h.

17. Read only Files
× A file that's read-only can be
opened and viewed like any
other file but writing to the file
won't be possible.
× In other words, the file can only
be read from, not written to.
Hidden files
× A fil whose name dose not
apper in the directory search.
× Hiding files provides security in
situation where several people
use the same mechine.
× May not be run on Dos V2.
Dos system files
A DOS file that contains the
fundamental part of DOS .
EG:
IO.SYS (or IBMBIO.COM): This
contains the system initialization
code and built-in device drivers.
Volum Label
× Disk drive volume label.
Attribute is read-only.
× A volume label, is a unique
name assigned to a hard drive,.
× a volume label is not required
but it's often useful to give a
name to a drive to help identify
its use in the future.
subdirectory
× A subdirectory is
a directory that is located
within another directory. A
similar term can be used to
describe a folder beneath
another folder in a graphical
user interface (GUI
Archive bit
× Used by backup commands.
× Set when file created.
× When the file is saved by
BACKUP,this bit is cleared .
× Changing the file cause the
archive bit to be set again.

18. THANKS!
Any questions?
You can comment below

19. Special thanks to all the people who made and
released these awesome resources for free:
×https://www.computerhope.com/jargon/h/hierfile.htm
×https://www.computerhope.com/jargon/d/director.htm
×https://www.lifewire.com/volume-label-2626045
×https://dictionary.cambridge.org/dictionary/english/file-directory
×www.utica.edu/faculty_ staff/qma/harddrive.
×https://www.google.com.pk/search?dcr=0&biw=1326&bih=668&tbm=isch&sa=1&ei=_ qFQWu_ xAZDMvwT
Du6Qo&q=attributeb+byte&oq=attributeb+byte&gs_ l=psy-
ab.3..0i13k1l2j0i13i5i30k1j0i8i13i30k1l7.134787.139689.0.140105.15.13.0.0.0.0.882.1644.3-2j6-
1.3.0....0...1c.1.64.psy-ab..12.3.1642...0j0i67k1.0.0Er6BIShV2U#imgrc=ai8JntaBNF6AbM:
×https://msdn.microsoft.com/en-us/library/aa445266(v=vs.60).aspx