"Linux now spans the spectrum of computing
applications, including IBM's tiny Linux wrist watch, hand-held
devices (PDAs and cell phones), Internet appliances, thin clients,
firewalls, industrial robotics, telephony infrastructure equipment,
and even cluster-based supercomputers. Let's take a look at what
Linux has to offer as an embedded system, and why it's the most
attractive option currently available.
The computers used to control equipment, otherwise known as
embedded systems, have been around for about as long as computers
themselves. They were first used back in the late 1960s in
communications to control electromechanical telephone switches. As
the computer industry has moved toward ever smaller systems over
the past decade or so, embedded systems have moved along with it,
providing more capabilities for these tiny machines. Increasingly,
these embedded systems need to be connected to some sort of
network, and thus require a networking stack, which increases the
complexity level and requires more memory and interfaces, as well
as, you guessed it, the services of an operating system.
Off-the-shelf operating systems for embedded systems began to
appear in the late 1970s, and today several dozen viable options
are available. Out of these, a few major players have emerged, such
as VxWorks, pSOS, Neculeus, and Windows CE."