page_title: Embedded system
section_title: User interfaces
hierarchical_section_title: Embedded system / User interfaces
caption_attribution_description: Digital clock of a premium design. This clock uses digital tuning, and offers various white noise sounds. Photo shot by Derek Jensen (Tysto), 2005-September-30
context_page_description: An embedded system is a computer that has been built to solve only a few very specific problems and is not easily changed. The word embedded means it is built into the system. It is a permanent part in a bigger system. It usually does not look like a computer, often no keyboard or monitor or mouse. But like any computer it has a processor and software, input and output.
  For example, the controller embedded in an elevator tells the motor to move the elevator to different floors, based on buttons that are pushed. A decoder is embedded in a satellite television set-top box to read a signal from the dish and send something that a TV understands. Often this type of system must do its work in a specific amount of time. This is called real-time computing. If a set-top box got interrupted to do another task, you would see a bad picture on the TV, for example. A general purpose computer will often have short pauses while it does something else, it is not real-time.
  Embedded systems control many of the common devices in use today, such as card readers in hotel door locks or several things in a car.
context_section_description: Embedded systems range from no user interface at all — only sending and receiving electric signals — to a full graphical user interface like on a modern computer. Quite often they will have a few push-buttons and a small display and some LEDs. A more complex system may have a touch screen, allowing the meaning of the buttons to change with each screen as in smart phones.
caption: An example of a user interface with buttons and a simple LCD display.
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