CS609 Current Final Term Fall 2013 File 3

AOA,

My today paper

80% mcqs from moaz file:

Subjective question:

1)Write three Data Structures for Memory DOS use?
Ans
• MCB ( Memory Control Block )
• EB ( Environment Block )
• PSP ( Program Segment Prefix )

2)Scan Disk Surface Scan for Bad Sectors

• It attempts to write a block.
• After write it reads back the block contents.
• Performs the CRC test on data read back.
• If there is an error then the data on that block is not stable the cluster of that block should be marked bad.
• The cluster is marked bad by placing the appropriate code for bad cluster so that they
may not be allocated to any file.

3) How Accessing NTFS volume in DOS?

• NTFS volume can not be accessed in DOS using DOS based function like absread( ) etc.
• DOS device drivers does not understand the NTFS data structures like MFT etc.
• If NTFS volume is accessed in DOS, it will fire the error of Invalid Media.
4) How to recovered a Deleted Files?

• 0xE5 at the start of file entry is used to mark the file as deleted.
• The contents of file still remain on disk.
• The contents can be recovered by placing a valid file name, character in place of E5 and then recovering the chain of file in FAT.
• If somehow the clusters used by deleted file has been overwritten by some other file, it cannot be recovered.

5) Structure of Partitioning Table

• Total size of Partition Table is 512 bytes.
• First 446 bytes contains code which loads the boot block of active partition and is executed at Boot Time.
• Rest of the 66 bytes is the Data part.
• Last two bytes of the Data part is the Partition table signature.

6)Find root dir if reserved sector = 1 and size of fat is 9?

Root DIR Sector: reserved sectors +
2 * (size of FAT) = 1 + 2 * 9 = 19

7)write the functionality of absread and abswrite?

• absread( )
is used to read a block given its LSN
• abswrite( )
is used to write a block given its LSN
absread(int drive, int nsects, long lsec, void *buffer);
abswrite(int drive, int nsects, long lsec, void *buffer);

other question from old papers. Kindly pray for me :)