An Operating System, in short : OS, assure the management of a computer and its peripherals, the material parts allowing to carry out particular functions (keyboard for the seizure of texts, mouse for movement, CD or DVD drives for reading of storage medium, printers for printing, monitors for visualization...).
An OS is in charge of making the connection between the material resources of a computer, the user and the applications (word processor, video game...). So when a program wishes to reach a material resource, it is not necessary to it to send specific information to the peripheral, it just has to send the information to the operating system, which takes care to pass on them in his turn in the peripheral concerned via its driver. The driver avoids to every program recognizes and takes into account the communication with every type of peripheral.
OS’s makes certain number of preparatory operations to assure the exchanges between the processor, the memory and the physical resources grouped together under the general term of peripherals.
They are constituted by a set of calls system used by all programs and a whole range of tools to the arrangement of the user and the main thing of which is an interpretor of language of command called Shell.
Tasks of operating systems
An operating system makes two very different tasks :
- Present a virtual machine to the user.
That is transform a set of components and of electronic circuits into a modern tool which offers a simple abstraction at the level of entrances / exits, of use of the memory, the management of files, protection and control of the errors and the interaction of the programs between them.
- Manage the resources of a computer.
That is share the resources and avoid the conflicts of use of the memory, the peripherals and network interfaces.
Functions of operating systems
We can divide the functions of classic operating systems into four main parts :
- 1. The management of the processes (programs).
- 2. The management of the memory.
- 3. The system of files.
- 4. The management of entrances / exits.
History of operating systems
The history of the computing is short and nevertheless, it knew big evolutions. It is confidentially connected to the evolution of the computing. We can present it separated in four big stages :
- 1. First generation (1945 - 1955) : vacuum tubes.
- 2. The Second generation (1955 - 1965): transistors and batch processing.
- 3. The Third generation (1965 - 1980) : integrated circuits and multiprogramming.
- 4. The Fourth generation (1980 - today) : microcomputers
