A process which requires accuracies of both results of processing and output, as well as depending on the output time, is called a realtime process. And the system which deals with the realtime process is called a Real-Time System. That is to say, a realtime system, requires a correct output result, as well as a adequate time for outputting the result. Typically, when an event occurs, it is essential to make the response in a required time frame, and that time is called a deadline. Consider a very simple example of realtime system, which is the computer system for controlling the automobile’s brake. It is obvious to say which system is better: a system that stops the car in 1 second for 99.99% cases, but the remaining 0.01% cases will cost 10 seconds, or a system that always stops the car in 2 seconds.
A system, that is embedded in all kinds of devices, controlling them, is called a device-embedded control system, or just embedded system. In what way, or the matter about what is actually embedded, is still undefined, we could still just simply think of a appearance that doesn’t look like a computer, although this kind of description is still vague.
With the development of semiconductor and microprocessor technology, embedded system is becoming widely used inside the electronic and electrical devices around us. Here’s a table that shows some examples of embedded system application.
Audio & Video Systems - Television, Video, Digital Camera, Set-top box, Audio Systems.
Home Appliance - Microwave oven, Rice Boiler, Air Conditioner, Laundry Machine.
Personal Information Device, Entertainment & Education Device - PDA, Electronic Notebook, Car Navigation System, Game Console, Electronic Musical Instrument.
PC Accessories - Printer, Scanner, Desktop Computer, CD-ROM Drive.
OA Equipment - Copy Machine, FAX, Word Processor.
Communication Devices - Answering Phone, ISDN Phone, Mobile Phone, PHS, ATM Switch, Broadcasting Equipment & Device, Wireless Equipment, Man-made Satellite.
Transportation Machinery - Automobile(Engine Control, ABS, Airbag), Train Control, Aircraft Control.
Industrial Control, Others - Plant Control, Industrial Robot, Elevator, Vending Machine, Medical Equipment, Data Terminal for Business.
Looking forward, with the increasing application of embedded systems in all kinds of equipments, as well as the highly functionalized and complicated control objects, it is considered, that embedded system is going to become even larger and more sophisticated. Also, the trend of digitalising devices will make embedded systems even more important. At the same time, we think that it will be highly demanded embedded systems should connected within network.