"I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image."
-Stephen Hawking.

A computer virus is only a program, similar to other computer programs. The only difference is that it is destructive. Stephen Hawking has said rightly that computer viruses should count as life. It clearly resembles the destructive aspect of human nature.

A computer virus is a computer program that can copy itself, and infect other computers. Other "destructive" computer programs like malware, spyware, adware, etc are also counted as viruses, but they are different, technically, from actual viruses. Many viruses have become famous in the past, by wreaking havoc in the field of computer industry. The viruses like Melissa virus in 1999, I Love You virus in 2000, Mydoom worm in 2004,Storm worm in 2007 etc have been famous for their destructive behavior.

What is a Virus?
A virus is a small piece of software that hides inside other software. For example, the virus may attach to a word document and spread itself to other files or programs when that document is accessed, and wreak havoc.






Types of virus

E-mail viruses
An E-mail virus travels through the e-mail messages, and replicates itself over by automatically mailing itself to the people in the victim's e-mail address book.

Trojan horses
A trojan horse is simply a computer program that claims to do one thing (it may claim to be a game) but instead does other things like damage some hardware or delete the files on the hard disk. They do not replicate automatically.

Worms
A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of it scans the network for other security limits, and when it finds one, it copies itself to the new machine and starts replicating from that machine as well.


Computer viruses are so called because they share some of the traits of the biological virus. They pass from one computer to another, infecting each one, as the biological virus does. There are very few reasons for the existence of such virus. The first reason is the same psychology that drives the vandals and arsonists. Someone who likes to break a window on someone's house, paint signs (usually vulgar signs) on walls and buildings or burn down a beautiful forest seems to be a psychological thrill. Such persons enjoy doing damage. And computer virus is a very safe means of damaging other people's properties or whatsoever.

The second reason builds up from the pleasure of watching things blow up. Most people enjoy watching skyrockets. They are also fascinated with things like explosions and car wrecks, the reason why most movies nowadays have such scenes. Creating a computer virus is similar to that, and its a little different kind of explosion that more people would love to watch.

The next reason involves bragging rights, or the thrill of doing it. If one finds a new thing, like a big ancient tree that no one else has ever seen, he can "tell" about the tree to other people, or he can "show" them, to be the first to discover that tree. The computer virus is a means of showing that security hole in the computer system that no one else has detected before.

Recovery from viruses

Anti-virus software

An anti-virus software, as the name implies, works against the viruses - it helps to prevent the infection of the computer from the viruses, and if the computer is already infected, it helps to heal the computer by removing the virus, or in some cases, removing the infected file itself.
An anti-virus works mainly in two ways. The first and the most common method of detecting the virus is using a list of virus signature definitions. This works by comparing the contents of the computer's memory (RAM and boot sectors), and the files stored on fixed or removable drives against the database of known "virus signatures".

The second method is using heuristic algorithm to detect the viruses on the basis of the common behaviors that most of the viruses exhibit.

System restore

The system restore is a built-in feature of all windows family. It restores the registry settings and other critical system files and settings to a previous pre-set checkpoint. The checkpoint may be created by the system itself, during installation of hardwares and softwares, or it may be created manually by the user. But the defect of this method is that the files to restore the system are also saved on the hard disk itself, which may as well be infected by the virus.

Operating system re-install

Re-installing the operating system itself is another efficient method of virus removal, because while doing so, all the previous files stored on the hard disk on the partition where the operating system was, are deleted. But care must be taken in re-installing the operating system, because the new OS installation files may already be infected with viruses, and in addition to the system partition, other partitions of the hard disk may also be infected with the virus.

Hardware is any part of the computer that can be seen and touched. Mouse, keyboard, monitor, CPU, etc fall under this category. Following are the most common hardware that are in use everyday.

CPU (Central Processing Unit)

A CPU is considered as the brain of the computer. It indeed is, because all the controlling and "thinking" works are done by this part of the computer. Early computers needed to be physically wired again and again in order to perform different tasks, but with the introduction of stored program architecture of computers, the whole definition of CPU was redefined.

Monitor

A monitor or screen or visual display unit(VDU) displays the inputs that is being fed to the computer, and the outputs the computer generates. Monitors were part of the computer only from 1970s, and since then, they have observed a vast variety in size, price and capabilities.

First Generation (1940-1956) Vacuum Tubes

The computers of first generations used vacuum tubes and magnetic drums, and were large enough to fill an entire room. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions.

Depending on machine language, the lowest-level programming language understood by computers to perform operations, the first generation computers could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts.






The invention of transistor by William Shockley, John Bardeen, and Walter Brattain in 1947 led to an entire new generation of computers.
Although invented in 1947, the transistor was used in computers only in the late 1950s. The transistor allowed the computers to become smaller, faster, cheaper, more energy-efficient and more reliable than the first-generation. The transistor was a superior improvement over the vacuum tubes but still, it generated a lot of heat. Second generation computers still relied on punched cards for input and printouts for output. 
 
Third Generation (1964-1971) Integrated Circuits

The invention of integrated circuit (IC) began the era of third generation of computers. A large number of transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers. 
 



A microprocessor is a device that consists of thousands of integrated circuits built onto a single silicon chip. The microprocessor brought a whole new era of the generations of computers. The first generation computers filled an entire room, and now there were fourth generation computers that could fit in the palm of the hand. The Intel 4004 chip, developed in 1971, fitted all the components of a computer, central processing unit to memory and input/output controls, on a single chip. 
 



Fifth Generation (Present and Beyond) Artificial Intelligence
 
Fifth generation computers are based on artificial intelligence, which are still under development. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. Nanotechnology is radically changing the face of computers. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization.

Computer has been the most important invention of man, yet. It differs largely from other inventions that have been changing human lifestyles. Started with simple calculations, this masterpiece of the human civilization has been serving the humans since a long time. From its large mainframe predecessors to the modern age laptops, computers have been an integral part of human life.

The history of computer has a large variation, in terms of size, shape, power consumption and operating capabilities. Early computers needed a separate room for their installation. They were too expensive to be used by the general public. But their demand in the computing areas forced them to be small, cheap and flexible.

A simple computer

A lot of terms are used to describe the computers, most of which imply the size, expected use or capability of the computer. The term computer can apply to any device that has a microprocessor in it, but in view of a general public, a computer is an electronic device that receives input from the user through a mouse or keyboard, processes it in some way and displays the result on the screen.