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The Internet

What is Internet?

The internet is a chain of interconnected computer networks using the standard internet protocol suite (TCP/IP). This chain is comprised of web servers and client computers. Clients are computers that access this network through an internet connection. Web servers handle the actual web pages. Web servers have a bunch of web sites loaded waiting for clients to request them, which is done through browsers such as Internet Explorer, Firefox, Opera, etc.

The Internet is a network of networks, spread over the whole globe. The foundations for the origin of the Internet were laid back in the 1960s when the United States funded research projects of its military agencies to build robust, fault-tolerant and distributed computer networks. Initially, the network was known as ARPANET, which later became the internet when its capacity was increased with the connection of more number of computers to the network.The Internet has no centralized governance in either technological implementation or policies for access and usage.

The Internet
fig: The Internet

The most important component of the Internet is the Internet Protocol (IP), which provides addressing systems (IP addresses) for computers on the Internet. The IP address is a unique naming convention of each and every computers that are part of the Internet.

The Internet has been serving everyone around the world, with every possible means. E-mail is an important communications service that is available on the Internet. The concept of sending electronic text messages among the people similar to the mailing letters or memos predates the creation of the Internet. File sharing helps to send and receive large sized files across the globe. The Internet has also enabled entirely new forms of social interaction, activities, and organizing, through social networking sites such as twitter, facebook, myspace, etc.

Computer Virus

"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.

fig: Computer virus (illustrative)

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.

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.

Computer hardware

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.

The introduction of the microprocessor in the 1970s significantly affected the design and implementation of CPUs. Since the introduction of the first commercially available microprocessor in 1970, this class of CPUs has almost completely overtaken all other central processing unit implementation methods. Combined with the vast success of personal computers, the term "CPU" is now applied almost exclusively to microprocessors.


fig.: A CPU


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.

fig. A modern monitor

There are various types of monitors, each with their own features. Following are the types of monitors:

CRT monitor

A CRT (Cathode Ray Tube) monitor consists of a "cathode ray tube" at the back of it. It supports high dynamic range (up to around 15,000:1), excellent color, wide gamut (set of colors) and low black level (evel of brightness at the darkest (black) part of a visual image). It can display natively in almost any resolution and refresh rate. It does not have input lag, response time is sub-milliseconds and almost zero color, saturation, contrast and brightness distortion.

On the contrary, CRT monitors usually have large size and weight, especially for bigger screens, high power consumption and produce noticeable flicker at low refresh rates.

CRT monitorfig: CRT monitor

LCD monitor

LCD monitors are famous for being very compact, light weight and small size. They have lower rate of power consumption, no geometric distortion and little or no flicker depending on backlight technology.

LCD monitors have limited viewing angles, which cause color, saturation, contrast and brightness to vary, by the variations in posture. They have slow response time, only one native resolution, and dead pixels may occur during manufacturing or through use.

LCD monitor

fig: LCD monitor

Plasma monitor

Plasma monitors are compact and light, with high contrast ratios (10,000:1 or higher), excellent color, wide gamut (set of colors), and low black level. They also have high speed response, almost zero color, saturation, contrast or brightness distortion, excellent viewing angle and no geometric distortion.

On the other hand, they have large pixel pitch, which means that the resolution is either low or a large screen is necessary. Flicker is noticeable when viewed at close range. Operating temperature and power consumption are high and only one native resolution is supported. They have noticeable input lag, and dead pixels are possible during manufacturing.

Plasma monitor
fig: Plasma monitor


A mouse is a pointing device with two or more buttons on it. It sometimes consists of other features like wheel that allows a user to perform various system-dependent operations, or add more control or dimensional input. The motion of the mouse is corresponded to the motion of a cursor on the screen, known as "mouse pointer", allowing a fine control of the Graphical User Interface (GUI).

mouseThe name mouse, which originated at the Stanford Research Institute , is derived from the resemblance of early models (which had a cord attached to the rear part of the device, suggesting the idea of a tail) to the common mouse.

Types of mouse

There are many types of mice so far. Most common of them are mechanical mouse, optical mouse and inertial mouse.

Mechanical mouse
Mechanical mouse
A mechanical mouse consists of two rollers rolling against two sides of the
central rubber ball. One roller detects the forward–backward motion of
the mouse and other detects the left–right motion. The motion of
these two rollers causes two disc-like encoder wheels to rotate, interrupting
optical beams to generate electrical signals. The mouse sends these signals
to the computer system by means of connecting wires, or wirelessly
through bluetooth. The driver software in the system converts the
signals into motion of the mouse cursor along X and Y axes on the screen.

Optical mouse
An optical mouse utilizes light emitting diodes and photo-diodes to detect the movements relative to the underlying surface, instead of moving a part of it, as in a mechanical mouse.

Optical mouse An optical mouse uses optoelectronic sensors to take successive images of the surface on which the mouse operates. With the improvement on the image processing technologies, modern mice are equipped with the image processing chips itself, embeded into them. This give them the ability to detect the motion on a wide variety of surfaces, translating the movement of the mouse into the movement of the mouse pointer and eliminating the need for a special mouse-pad. Using light emitting diodes (LED) or laser diodes, optical mice illuminate the surface under them. Changes between two consecutive frames are processed by the image processing part of the chip and translated into movement on the two axes using and optical flow estimation algorithm.

Inertial mouse

An inertial mouse uses a tuning fork or other accelerator (device to measure proper acceleration, which is the acceleration it experiences relative to freefall), to detect the motion for every axis provided. The user requires only small wrist rotations to move the cursor, which reduces fatigue . They are usually cordless, often having a switch to deactivate the movement circuitry between use, allowing the user the freedom of movement without affecting the cursor position.


A keyboard is an input device, which is similar to a typewriter. It consists of keys or buttons to give instructions to the computer. Most keyboard keys produce letters, numbers or characters; other keys or simultaneous key presses can produce actions or computer commands. Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features.

fig. keyboard

Modern keyboards are equipped with much larger number of keys, including special purpose keys. Such keyboards are known as multimedia keyboards.

A keyboard consists of many types of keys. These include alphakeys (alphabets), numeric keys (numbers), function keys (keys F1 to F10 or F12) and other special purpose keys like Shift key, Control key, Alt key, Enter key, etc.

Hard disk

A hard disk is a secondary memory device of a computer. It consists of magnetic plates arranged one above the other. A motor is present to allow the reading of the data stored on the plates, to allow the rotation and movement of the head (the part that reads data from the magnetic plates).

A hard disk stores data by magnetizing the ferromagnetic material in it, to represent either a 0 or 1 binary data. The data is read back by detecting the magnetization of the material.

hard disk

Inside hard disk

fig. Inside the hard disk

fig. A hard disk

Generations of computers

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.

Generations of computers
fig.: A vacuum tube

Second generation (1956 - 1963 ) Transistors

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. 
Second-generation computers used assembly language instead of the machine level language, which allowed to specify the instructions in words having specific meanings, called mnemonics.
High level programming languages like COBOL( COmmon Business Oriented Language ) and FORTRAN ( FORmula TRANslation ) were also under development at this time.

Generations of computers
fig.: Early transistors

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. 
The third generation computers used keyboards and monitors for input and output respectively. They used operating systems to interface with the users, which allowed them to run many different applications at a time.

Generations of computers
Generations of computers

fig.: Integrated Circuits

Fourth Generation (1971-Present) Microprocessors

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. 
With the passage of time, these small computers became more and more powerful, and they were linked together to form networks, which in turn led to the development of the Internet. It was also in the fourth generation computers that GUIs, mouse and other handheld devices were introduced.

Generations of computers
Generations of computers

Fig.: Microprocessors

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.