Generally speaking, it is known that a computer is a complex device, which operates with information. Several decades have passed since the first computers used by man appeared, but from the first computers and until today, all the computers are operating based on meeting several key tasks:

- processing the information

- saving the information

- transfer and communication of information

As it’s seen, the computer is just an instrument which the user uses in order to process, save, transform and to circulate useful information in their work and life.

Processing information

A computer is basically a calculator, and the first impression about its basic role is that is it used to calculate. In fact, what it does is process information, and this means that it transforms useful information into other useful information, from a form to another. The processing involves a lot of mathematical calculations executed by the computer, and many other operations.

The information with which the computer is permanently in touch can be split in 3 categories:

Data – are those information which are processed. For example, a computer can display in which day of the week is a certain calendar date (represented by day, month and year). For this, it has to receive the calendar date, after which is it processed and will display the day of the week corresponding to that date. The introduced calendar date and the displayed week day are data with which the computer operated in this process. The text documents, images and even sounds, are also from Data category, with which the computer operates and  whose handling and processing represent mostly the purpose for using the computer at a desk activity.

Programs – represents a special data category, which contains algorithms according to which the computer will process data. The computer is a simple electronic device, but according to the programs it uses, it will be able to process the data received in different ways. For example, in the previous example it was necessary for a capable program to exactly calculate which in which day of the week is a certain calendar date, considering all the calendar’s details (leap years, the days of each month, etc.), according to a well established mathematical algorithm. The programs are made from instructions which are executed, one by one, until, starting from the introduced data, the final result appears. For a computer, these instructions are encoded in a machine-code, a programming language used rarely even by the experts. The speed with which the instructions are executed, reached very high today, that when we push a key, one letter appears to the screen instantly