embedded systemAny 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.)|
Computer systems that cannot be programmed by the user because they are preprogrammed for a specific task and are buried within the equipment they serve. The term derives from the military, where computer systems are generally activated by the flip of a switch or the push of a button. The continual increase in the densities of ever-smaller microprocessors, on silicon chips that fit on a thumbnail, and the attendant decreases in their costs, has pushed the concept of embedded systems well beyond the original military applications. Embedded systems are also used in industrial, automotive, consumer, and medical applications.
Most embedded microprocessors are of the CISC (complex-instruction-set computer) type, and most of these are used in applications where low cost is paramount and performance is secondary, such as consumer products. The later-generation microprocessors have wider bus widths, up to 64 bits, and thus can do more computations.
Since about 1990, microprocessors of the RISC (reduced-instruction-set computer) type have appeared, with much greater computational capability and at greater cost. RISC processors are used mostly in those embedded applications where performance is primary and low cost is secondary. They are used in engineering workstations, where the computational burdens of high-resolution graphics require such processors. See Computer-aided engineering, Computer graphics, Computer systems architecture