Virus
A Virus is an actively infections, malicious computer program that place copies of itself into other applications and programs, but not data files or documents. The reason why a virus attaches itself to an executable program is in order to perform destructive action. It has to get executed. Thus, it remains dormant until a user runs the application or program to which it is attached.
When a virus-infected program is executed it leads to the infection of all portions of the memory and then infects the files on the disks. So this is how it may lead to infection of a disk on another computer and thereby spreading the virus through the new system leading to a loss of stored information or data.
A computer virus is basically a program written for destructive purpose. It is written in such a way that it can enter the computer without knowledge of the of the machine or the user. It enters the machine through an infected floppy or a program. It has therefore the capability to make prefect couples of itself and cause abnormal functioning of the machine.
Viruses
are brain works of intelligent programmers who are well averse with the intricate
chip level manipulation of codes Effects of a virus infection-
1) Corrupt files leading to data loss.
2) Increase files sizes.
3) Interference with display on the monitor.
4) Formatting of the Hard Disk thereby destroying data.
5) Destroying the File Allocation Table.
6) Slowing down of the system.
7) Marking good sectors as bad.
8) Frequent hanging of machines.
BOOT-SECTOR
OR PARTITION:
Table virus; A boot-sector virus replaces itself for the bootstrap loader and
a partition table virus substitutes itself for the master boot program. This
makes such various get loaded every time the machine is switched on. When the
virus gets loaded into RAM. It goes infecting all the files on the disk. Also
to show that the processing of data is going on normally the virus transfers
control to the original bootstrap loader so that the booting procedure can take
place normally. Some examples of boot sector/partition table viruses are (c)
Brain. PC tone and ? Birthday Joshi. Other example are 13th Friday, Alabama,
Ping-Pong ball virus (bouncing ball). Dark Avenger, BOXA virus, etc.
MS-DOS 6.22
DISK OPERATING SYSTEM act as an interface between user and the computer. Did operating system the programs that manage the disk operating and memory location. Managing the disk operation involves reading, writhng, searching, and shorting etc. the contents on to, the disk other operating systems are UNIX, XENIX, OS/2 etc.
EVOSUTION
OF DOS.
The home computers were very successful in USA and this inspired IBM (international
business Machine) to introduce small computers (PC' s or Personal computers)
into the market. They also wanted and operating system for their Pac range.
Mr. Bill Gates of Microsoft purchased the copyright of an operating system called
Q DOS (Quickly and dirty Operating system), which was developed by Mr. Tim Peterson
and used that as a basic for another operating system known as MS-DOS. There
was an understanding between Microsoft and IBM and copy of MS-DOS is sold which
every IBM computer.
WHAT IS PC-DOS?
PC-DOS and MS-DOS both refer to the same operating system. The only difference is that IBM has manufactured PC-DOS and Microsoft has manufactured MS-DOS.