What is cpu?

The CPU (Central Processing Unit) is the brains of your computer and consists of ALU (Arithmetic Logic Unit), which carries out the instructions of a program to perform arithmetical and logical operations, and CU (Control Unit), which controls the system and coordinates all the operations. In order to memorize input and output data, there is an internal memory that can be distinguished into volatile and non-volatile. Volatile memory is memory that loses its contents when the computer or hardware device is off. Computer RAM (Random Access Memory) is a good example of volatile memory. It is the main memory of the computer where all data can be stored as long as the machine is on. On the contrary, a non-volatile memory contains information, data and programs that cannot be modified, or can be modified only very slowly and with difficulty. Computer ROM (Read Only Memory), for example, contains essential and permanent information and software which allow the computer to work properly. Memory storage devices are available in different options, sizes and capacities. These devices are extremely useful; they can be rewritten and offer incredible storage capacity, up to 256 GB. They can be magnetic (hard disks), optical (COs and OVOs) or solid (flash memory cards) .

The types of computer

Desktop: this is a personal computer intended for regular use at a single location. It's designed to sit on your desk, and as such it consists of a monitor and a tower with extra drives inside. Laptop: this is a portable computer, which integrates all the usual components of a desktop computer into a single unit. Smaller versions of laptops are known as notebooks. It is useful for people who do not have a fixed place to work at. They are lighter and handier than desktop computers, but they also tend to be more expensive. They require an expensive battery that needs to be recharged quite often.

Netbook: this is a portable computer, with limited capabilities as compared to standard laptops. It is smaller and lighter, but it also has less processing power than a full-sized laptop. It is useful for people who don't have a fixed place to work at or for those who travel, but still need to surf the Net. They use a battery which needs to be recharged often.

Palmtop: this is a small portable computer designed to have large amounts of information close to hand. They are provided with light long-lasting batteries and special operating systems. They don't require any keyboard but use special pens or touch screens to enter data and access information.

Internet

The Internet is a worldwide information system consisting of countless networks and computers, which allow millions of people to share information and data. Thanks to the Internet it is now possible for people all over the world to communicate with one another in a fast and

cheap way. The Internet was first invented in the 1960s in the USA by the Department of Defence as an internal project to link computers. The Department wanted an extremely safe way of sending messages in case of nuclear attack. It was a British physicist, Sir Timothy Berners-Lee, who used it to make information available to everyone and created the most important media of the 21 st century. In 1980 while working at CERN in Geneva - the largest particle physics laboratory in the world - he first thought of using hypertext to share and update information among researchers. Then in 1989-90 he produced a plan to link hypertext to

the Internet to create the World Wide Web. He designed and built the first site browser and editor, as well as the first web server called httpd (Hypertext Trasfer Protocol Deamon).