An operating system is made up of software instructions that lie between the computer hardware and the application programs. At the center is the kernel which provides the most basic computing functions. Associated with the kernel are a variety of basic services needed to operate the computer. These include:
- File systems: The file system provides the structure in which information is stored on a computer. Information is stored in files, primarily on hard disks but also on removable media such as CDs and DVDs. Files are organized with a hierarchy of directories.
- Device drivers: These provide the interfaces to each of the hardware devices connected to your computer. A device driver enables a program to write to a device without needing to know details about how each piece of hardware is implemented. The program opens a device, sends and receives data, and closes a device.
- User interfaces: An operating system needs to provide a way for users to run programs and access the file system. For example, in Linux GNOME and KDE provide graphical user interfaces.
- System services: An operating system provides system services, many of which can be started automatically when the computer boots.
Without an operating system, an application program would have to know the details of each piece of hardware, instead of just being able to say, “open that device and write a file there”.
More information on operating systems: http://en.wikipedia.org/wiki/Operating_system
Authors bio is coming up shortly.