embedded system

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embedded system

[em′bed·əd ′sis·təm]
(computer science)
A computer system that cannot be programmed by the user because it is preprogrammed for a specific task and embedded within the equipment which it serves.

embedded system

Hardware and software which forms a component of some larger system and which is expected to function without human intervention.

A typical embedded system consists of a single-board microcomputer with software in ROM, which starts running some special purpose application program as soon as it is turned on and will not stop until it is turned off (if ever).

An embedded system may include some kind of operating system but often it will be simple enough to be written as a single program. It will not usually have any of the normal peripherals such as a keyboard, monitor, serial connections, mass storage, etc. or any kind of user interface software unless these are required by the overall system of which it is a part. Often it must provide real-time response.

Usenet newsgroup: news:comp.arch.embedded.

embedded system

Any electronic system that uses a computer chip, but that is not a general-purpose workstation, desktop or laptop computer. Such systems use microcontrollers (MCUs) or microprocessors (MPUs), or they may use custom-designed chips. Deployed by the billions each year in myriad applications, the embedded systems market uses the lion's share of electronic components in the world.

Embedded systems are employed in cars, planes, trains, space vehicles, machine tools, cameras, consumer electronics, office appliances, network appliances, cellphones, GPS navigation as well as robots and toys. Low-cost consumer products can use microcontroller chips that cost less than a dollar. See microprocessor and microcontroller.

All Kinds of Operating Systems
There are embedded versions of Linux, Windows and Mac, as well as other specialized operating systems. Embedded systems typically have limited storage, and an embedded OS is often designed to work in much less RAM than a desktop OS. They also typically work in real time. Small embedded systems may contain their own input/output routines and not require a separate operating system at all.

Programs Are in Firmware
In embedded systems, the software typically resides in firmware, such as a flash memory or read-only memory (ROM) chip, in contrast to a general-purpose computer that loads its programs into random access memory (RAM) each time.

Sometimes, single board and rack mounted general-purpose computers are called "embedded computers" if used to control a single printer, drill press or other such device. See embedded market, smart car, Windows CE, Windows XP Embedded, Embedded Linux and embedded language.

Embedded Systems in a Car
In 1968, Volkswagen used a microprocessor to control the fuel injection, making it the first embedded system in a car. Thirty years later, the Volvo S80 featured 17 systems controlled by a computer (the list above). Today's cars can have a hundred or more CPUs, and the electronics cost more than the steel.

Embedded in a Shoe!
The microprocessor in this sneaker calculates the pressure between the runner's foot and the ground five million times per second and continuously adjusts the comfort level (a motor lengthens and shortens a cable attached to a plastic cushioning element). (Image courtesy of adidas-Salomon AG.)