Levels of abstraction: A Real Life Example

• Users of a car do not need to understand how black boxes work
  
• Interaction of a black box with outside world is well-defined
  • Drivers interact with car using pedals, buttons, etc.
  • Mechanic can test that engine control module sends the right firing signals to the spark plugs
  • For engine control module manufacturers, transistors and capacitors are black boxes magically produced by an electronics component manufacturer
• Encapsulation leads to efficiency:
  • Mechanic deals only with car components (e.g. electronic control module), not with sensors and transistors
  • Driver worries only about interaction with car (e.g. putting gas in the tank), not about motor or electronic control module