Project 4 - Disk Structure Analysis

	For this project you will need to use the same diskette that was reformatted and returned to you from your handed-in Project 3. (If you did not hand in Project 3, you must provide a diskette to the instructor that will be reformatted and have some files loaded on it.)
	Write protect the disk before you begin your analysis.  Since you are analysing deleted file structures, anything you write to this diskette will over-write and damage the information for which you are looking.  (If you ignore this warning and do overwrite your disk, you will have to contact the instructor for a replacement and pick it up at the next class.  No extensions are granted for overwritten disks.)
	Shut down Windows.  Completely.  Use "pure" MS-DOS for this assignment.  You (probably) can't decode these disks if Windows is running.  You must restart your computer in "pure" MS-DOS mode.  (If you try using DEBUG to read these disks under some versions of Windows, you will get fatal disk errors: Abort, Retry, Fail?)  Do not use a DOS window inside Windows.  Restart the computer in MS-DOS mode.

1. Write protect your disk before you insert it.  This is extremely important.
   
2. Shut down Windows and start up your computer in MS-DOS mode.  (Using an MS-DOS window under Windows probably won't work.)
   
3. Use DEBUG to load a copy of the boot sector from your floppy disk into memory.  Display at least the first 20h bytes of the boot sector and either save a copy of this dump to a file (using output redirection on the MS-DOS command line) or print a copy of the screen directly (using Print Screen). If you choose to save to a file, you will need to print this file (using a Courier or Terminal fixed-width font) at the end of the project.
   
4. Based on the values supplied by the DEBUG dump, provide the following information in both hexadecimal and decimal (giving two numbers for each of the five values):

   Boot Sector Dump Value	Hexadecimal	Decimal
   the number of sectors per file allocation unit (cluster)
   the number of root directory entries
   the number of copies of the FAT
   the number of sectors used by each copy of the FAT
   the number of sectors per track

   
   
5. Calculate the absolute disk sector number of the first sector of the root directory.

   	Show clearly how you used the Boot Sector Dump information to calculate this value.
   	Give the absolute sector value in both hexadecimal and decimal (two numbers).

6. Using the absolute disk sector number that you just calculated, load the first sector of the root directory into memory.  (Remember to use only hexadecimal numbers in your commands to DEBUG!) Your DEBUG dump will show that this root directory once contained many odd file names, as well as holding the entries for the few not-deleted files you can still see left on your diskette (including the README file).

   	Display enough of this root directory to locate the entry for the deleted subdirectory named "Project Four Directory".  This name is the Windows95 long name of this subdirectory; ignore the long name entries.  You will have to locate its corresponding MS-DOS short name.
   	Save the DEBUG output showing this complete deleted directory entry to a file, or print your screen directly.

7. Examine the dump of the root directory entry of this deleted "Project Four Directory" subdirectory:

   From the dump, determine the starting cluster number of this "Project Four Directory" subdirectory.  Give the cluster number in both hexadecimal and decimal (two numbers).

   	Using that cluster number, determine the absolute disk sector number of the first sector of the "Project Four Directory" subdirectory itself.
   	Show clearly how you used the Boot Sector Dump information and the subdirectory's cluster number to calculate this absolute sector number.
   	Give this absolute sector number for the "Project Four Directory" subdirectory in both hexadecimal and decimal.

8. Using the absolute disk sector number you just calculated, load the first sector of the deleted "Project Four Directory" subdirectory into memory.

   	Save the DEBUG output showing the contents of this subdirectory to a file, or print your screen directly.  Note that the dump shows that this deleted subdirectory only contains deleted files.
   	In the dump of this subdirectory, locate the deleted file that was called "Find This File".  This name is the Windows95 long name of this file; ignore the long name entries.  You will have to locate its corresponding MS-DOS short name.
   	Calculate, using information in this subdirectory entry, the starting cluster number and then the absolute disk sector number of the first sector of this deleted file named "Find This File".
   	Show clearly how you used the Boot Sector Dump information and the file's cluster numbers to calculate this absolute start sector number.
   	Give this absolute sector number for the "Find This File" file in both hexadecimal and decimal.

9. Using the absolute disk sector number you just calculated, load the first sector of the "Find This File" file into memory.

   	Save the DEBUG output showing at least 70h bytes of the contents of this sector to a file, or print your screen directly.
   	You will recognize that you have found the right sector, because the ASCII dump will show the word "BINGO!" followed by your disk serial number as the first strings of the sector.

10. Using the disk geometry of your encoded floppy disk, calculate the location on disk in terms of Cylinder, Head (also known as side or surface), and track-Sector numbers (C/H/S) of absolute disk sector 84h.  Express the numbers in C/H/S in decimal, not hexadecimal. 

    	Show clearly how you used the Boot Sector Dump information and the absolute sector number 84h to calculate this C/H/S location.
    	Is the sector 84h located on the top side of your floppy disk or on the bottom side?

11. BONUS: Calculate the location on disk of the beginning of file "Find This File" in terms of C/H/S.  Express the numbers in C/H/S in decimal, not hexadecimal. 

    	Show clearly how you used the Boot Sector Dump information and the file's absolute sector number to calculate this C/H/S location.
    	Was the first sector of the "Find This File" file located on the top side of your floppy disk or on the bottom side?

	No diskettes!  Keep your encoded floppy as a souvenir.  Hand in only paper.
	Submit only clearly printed calculations on paper, in a format adhering to my usual assignment guidelines.  (Use the correct font for your DEBUG dumps.)
	Please pay attention to the required DEBUG output dumps for various steps, above.  You may wish to review how to do DEBUG dumps using output redirection on the MS-DOS command line.
	The print-outs and calculations of this project on paper must be delivered to the instructor (or under his office door at WB222B) no later than 10:30pm, Wednesday August 2, 2000.  No late assignments can be accepted.  (The term is over!)  Assignments completed and handed in by the end of class on Tuesday August 1 will be marked and emailed back before the final exam on Wednesday.
	Questions can be posted to the course news group.
	Make sure you reformat your encoded floppy before you try to re-use it for other data storage!