How large file contents can be managed using
FAT? 2 marks
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• Larger files would be comprised of numerous clusters. •
The first Cluster # can be read from FCB for rest of the Cluster, a chain is
maintained within the FAT.
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Answer
in simple words is in green
As
large files would be composed of many clusters the first Cluster number is
obtained from FCB and the subsequent clusters can be obtained from FAT by using
the previous cluster Number to obtain the next cluster number and so on.
When we talk about FAT32, what is the size of
FSInfo block? 2 marks
|
On a FAT32 volume, the FAT can be a large data structure,
unlike on FAT16 where it is limited to a maximum of 128K worth of sectors and
FAT12 where it is limited to a maximum of 6K worth of sectors.
|
FSInfo
block contains information required at the time of allocation/de-allocation to
the file. Size of FAT 32 is huge at allocation/de-allocation time so
calculating these values is not feasible, therefore these are stored in FSInfo
block
Which control information PSP contains? 2 marks
•
is situated before the start of a process.
•
contains control information like DTA ( Disk Transfer
Area)
and command line parameters.
Which is the location of timer count in BIOS data area? 2 Marks
Timer
location in BIOS data area is 40:6CH
Explain the purpose of file control block(FCB)? 3 Marks
Control
information about files are maintained in a data structure called the File
control
block
(FCB). The FCB for each file is created and stored in the disk.
We
can get information about the file such as size, date time of creation, data
time of last modification etc from FCB. Further we can also impose
restrictions on file such as read only, archived etc using FCB
In NTFS, where the backups of boot block are stored and why? 3
Marks
the NTFS "Backup Boot
Sector" isn't really part of the NTFS Volume; it's
actually stored in a sector immediately following the last sector of the
Volume, which makes an NTFS Volume's partition size 1 sector larger than its
Volume size!
What are three different kind of computer viruses? 3 Marks
Types
of Viruses
•
Partition Table Virus
•
Boot Sector Virus
·
• File Viruses
Write a C program that should print your name using int 21H with
the help of int86 function
See
Page#19 for idea solution detail
Idea
solution:
#include <dos.h>
union REGS regs;
main()
{
regs.h.ah = 0;
regs.h.al = 1;
int86( 0x10, ®s, ®s );
printf("Fourty by Twenty-Five color mode.");
}
What will be the impact of placing E5 in place
of first character of file name? 5 marks
|
DOS perform file deletion by placing 0xE5 at the first
byte of it FCB entry and placing 0’s (meaning available) in the entries for
the file clusters in the FAT.
|
How partition table virus fools DOS about conventional memory? 5
marks
•
DOS uses the conventional memory first 640 KB for its memory management The
transient part of Command.Com loads itself such that its last byte is loaded in
the last byte of Conventional Memory. If somehow there is some Memory beyond
Command.Com’s transient part it will not be accessible by DOS.
•
At 40:13H a word contains the amount of KBs in Conventional Memory which is
typically 640.
•
If the value at 40:13H is somehow reduced to 638 the transient part of
Command.Com will load itself such that its last byte is loaded at the last byte
of 638KB mark in Conventional RAM.
•
In this way last 2KB will be left unused by DOS. This amount of memory is used
by the Virus according to its own size.
Write down a TSR program, when ever user presses a key it displays
it thrice. For example if user has pressed “A” it will display “AAA”? 5 marks
#include
<dos.h>
void
interrupt (*old)( );
void
interrupt newfunc( );
void
main( )
{
old
= getvect(0x09);
setvect(0x09,newfunc);
keep(0,1000);
}
void
interrupt newfunc ( )
{
(*old)(
);
(*old)(
);
(*old)(
);
}
This
program simply intercepts the keyboard interrupt and places the address of
newint
in
the IVT. The newint simply invokes the original interrupt 9 thrice. Therefore
the
same
character input will be placed in the keyboard buffer thrice i.e three
characters will
be
received for each character input.
52.Find the root directory sector. Where reserved sector = 1 and
sector per FAT = 9. Use appropriate assumption where needed? 5 Marks
Root
DIR Sector: reserved sectors +
2
* (size of FAT) = 1 + 2 * 9 = 19
Objective 20 % from moaaz file and subjective 30 %
Q: what is differenc between tracks and sectors:
Q: Write disadvantages and advantages of FAT32:
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Q:How disk scan identify the
bad sectors?
|
|
Answer:- • 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.
|
|
|
Q# Suppose a disk is divided
into two partition and we have read MBR at LBA=0 to get information about
primary partition a) How many bytes of code part we need to skip to get
information about primary partition? b) How many bytes of code part we need
to read information?
|
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Q# Write down procedure to
convert a cluster number into sector number
Answer:- NTFS simply the following formula will be used to
translate the sector number into cluster number. Sector # = Cluster # *
Sector Per Cluster
|
|
Q: In FAT32, what is the size
of FSInfo?
Answer:- On a FAT32 volume, the FAT can be a large data structure,
unlike on FAT16 where it is limited to a maximum of 128K worth of sectors and
FAT12 where it is limited to a maximum of 6K worth of sectors.
|
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