The heart of computers is the ‘CPU’, the central processing unit. It controls all the processes in the computer. Everything that happens is broken down in simple datasets. Computers know only two switching states, which are expressed by numbers: 1 stands for ‘power on’, 0 for ‘power off’. All the data stored in the computer is encoded with different combinations of both these digits, the binary code – ‘binary’ means ‘two’. For instance, when we press ‘a’ on the computer, it is then converted into the number sequence 1100001: The last position stands for 1, the second last for 2, the third for 4, followed by 8, 16, 32, 64, and so on. The positions occupied by ‘1’ are counted, for the number sequence for ‘a’, it will be 1+32+64= 97. The code for ‘a’ is, therefore, 97. All data can be coded in this way – computers, therefore, actually calculate only with ‘1’ and ‘0’.
The film as the storage option for images was invented at the beginning of the 19th century. The researchers at that time were experimenting with toxic chemicals to store light reflected from the objects on a long-term basis. The Frenchman, Louis Daguerre, finally succeeded in 1837 to fix the images on a light-sensitive material in a salt bath. This was the first film. However, the exposure times were very long. People had to sit for a long time while the photographer captured their image on a photographic plate. The path to the film roll was paved in 1889 by the American George Eastman - a thin layer of silver salts was applied on flexible plastic celluloid. Digital cameras do not need this because they store everything on a computer chip.
Simulation programs are used for training in areas where the possibility of something going wrong is very dangerous. For instance, a trainee pilot does not fly an aircraft just after training. Before that he practices at a simulator, which behaves like an aircraft, but is on the ground so it does not crash if le pilot makes a mistake. We can also simulate a fault in a power plant or a tsunami. Trainees must demonstrate that they can handle he crisis effectively.
A CD-ROM is a plastic disc with a thin aluminium layer from which music, texts, and other data can be retrieved. Like everything else in the world of computers, these files are also stored in the numeric sequence of 1 and 0. In this case, there are tiny grooves for 1 or none for 0. A laser beam in the reader scans these grooves, which reflect the laser beam in different ways. From these laser reflections, the chip in the computer or in the CD player deciphers the data present on the CD, which could be music, text, photos, or complete programs.
In 1994, a climbing robot by the name of Dante II was sent for the first time to explore the interior of a volcanic crater in Alaska. After entry into the crater, the measuring devices and cameras, hidden in the legs of the robot, started exploring the dangerous terrain. By analyzing the data and the images received from the surroundings, an onboard computer calculated each step of the robot. It was able to overcome boulders as high as 1 m and descended 70 m deep in the volcano before crashing. Fortunately, it had sent all the data collected and the images to the research station via satellite before it crashed.
Many people transmit malicious viruses, mostly through e-mails. The virus is a small hidden program that deletes the data or destroys parts of the operating system, which controls the computer. The viruses then automatically go to other computers through e-mail addresses stored in our computer. Some protection is offered by the antivirus programs. The safest way to stop viruses entering your computer is not to open attachments from unknown senders, especially the ones with an unusual ‘subject’.
For reading on-screen texts the blind need a special reading line in Braille script. For this, the computer converts the text in electrical signals, which are then pressed upwards by the corresponding points in the reading line. The blind can then feel the Braille. Or the text can be read aloud to them by a special speech program – they can also dictate texts in the same way. In this way, the visually challenged can also surf on the Internet. Pictures must always be accompanied by text; otherwise the blind cannot ‘read’ them.
In 1969, some American universities and research institutes needed more computing power, and connected their computers with one another. Later, more and more computers got connected, giving rise to a worldwide network called the Internet. On the other hand, the ‘WWW’ – and the sending of e-mails – is a service, which is offered within the Internet. It is a worldwide association of information pages connected with one another called the ‘World Wide Web’. The basic requirement for searching in the WWW or for sending e-mails is access to the Internet, maybe through a telephone line. Surfing, i.e., searching for information, in the WWW is not possible without a special program called a browser which understands the language of the Web. The address of the website we want to look at is typed in the browser. For instance, the website 
The word ‘computer’ comes from the phrase ‘to compute’, or ‘to calculate’. Tools that help calculations, such as the abacus, have been around for the past 3000 years, but electronic computers that can perform complicated tasks at lightning speed appeared only about 70 year ago. Today, the world can no longer be imagined without computers. We enter commands with the help of keyboards and don’t stop to wonder at phrases like ‘open a window’ with the ‘mouse’. The world of ‘bits and bytes’ is also open to the blind. One has to be careful while downloading information from the Internet because malicious viruses can also be downloaded.
We need access to the Internet to send an e-mail. We can get the access by paying money to an internet service provider. In addition, one needs the email address of the receiver. The e-mail starts its journey when ‘Send’ is pressed from the sender’s email account. The e-mail then goes to the service provider, who sends from one ‘node’ to another, before it reaches its destination. It may happen that an e-mail sent from Berlin, goes to USA, then to India, and finally reaches your neighbour.