In all these ways, real-time systems support fast interaction with instruments and devices in the outside world.
EMBEDDED SYSTEMS
By far the most common type (by simple count) of operating system today is the embedded system.
Embedded systems lie within the automobiles, airplanes, thermostats, and other devices we use every day. It??™s
easy to overlook the fact that they are there, but our day-to-day lives are ever more dependent on such systems
to supervise the execution of the built-in programs for the microprocessors controlling everything from
dishwashing to transportation.
MANAGEMENT OF INPUT AND OUTPUT
The early operating systems consisted largely of a collection of code for device drivers. One could argue
that the most fundamental service of the operating system is to manage I/O, so that programmers can focus on
higher-level activity, and so that shared I/O devices are shared properly.
Strictly speaking, the operating system (or any software doing I/O directly) interacts with the device??™s interface
(or ???controller,??? or ???adapter???), rather than the device itself. Every I/O device such as a printer, disk, or mouse
connects to an interface, often a separate printed circuit board, and the interface connects to (plugs into) a bus
(an electronic connection path consisting of multiple lines) in the computer.
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