Datasheet

6 Part I: Getting Started in Red Hat Linux
about who owned the code, and the Internet was the primary communications medium. What,
then, were the conditions that made the world ripe for a computer system such as Linux?
What Is an Operating System?
An operating system is made up of software instructions that lie between the computer
hardware (disks, memory, ports, and so on) and the application programs (word
processors, Web browsers, spreadsheets, and so on). At the center is the kernel,
which provides the most basic computing functions (managing system memory,
sharing the processor, opening and closing devices, and so on). Besides the kernel,
an operating system provides other basic services needed to operate the computer,
including:
• File systems — The file system provides the structure in which information is
stored on the computer. Information is stored in files, primarily on hard disks
inside the computer. Files are organized within a hierarchy of directories. The
Linux file system holds the data files that you save, the programs you run, and
the configuration files that set up the system.
• 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. Linux has both graphical and text-
based user interfaces. GNOME and KDE provide graphical user interfaces,
whereas shell command interpreters (such as bash) run programs by typing
commands and options.
• System services — An operating system provides system services, many of
which can be started automatically when the computer boots. In Linux, system
services can include processes that mount file systems, start your network,
and run scheduled tasks. In Linux, many services run continuously, enabling
users to access printers, Web pages, files, databases, and other computing
assets over a network.
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.”
In the 1980s and 1990s, while Microsoft flooded the world with personal computers running
DOS and Windows operating systems, power users demanded more from an operating system.
They ached for systems that could run on networks, support many users at once (multiuser),
and run many programs at once (multitasking). DOS (Disk Operating System) and Windows
didn’t cut it.