Introduction to real time software systems script

Introduction to real time software systems script

• 1.
  Real-time Software Engineering SoftwareEngineering 10
• 2.
  Computers are usedto control a wide range of systems from simple domestic machines, through games controllers, to entire manufacturing plants.
• 3.
  The software inthese systems is embedded in system hardware, often in read-only memory, and usually responds, in real time, to events from the system’s environment.
• 4.
  Their software mustreact to events generated by the hardware and, often, issue control signals in response to these events.
• 5.
  Responsiveness in real-timeis the critical difference between embedded systems and other software systems, such as web- based systems or personal software systems.
• 6.
  In a real-timesystem, the correctness depends both on the response to an input and the time taken to generate that response.
• 7.
  If the responseto a stimulus in a real-time system is too late, the system is considered to be incorrect.
• 8.
  A real-time systemis a software system where the correct functioning of the system depends on the results produced by the system and the time at which these results are produced.
• 9.
  A soft real-timesystem is a system whose operation is degraded if results are not produced according to the specified timing requirements.
• 10.
  A hard real-timesystem is a system whose operation is incorrect if results are not produced according to the timing specification.
• 11.
  Embedded systems generallyrun continuously. They start when the system is powered up and do not terminate until the power is switched off.
• 12.
  Interactions with thesystem’s environment are unpredictable. Events may not occur when expected.
• 13.
  There may bephysical limitations, such as battery power, that affect the design of a system.
• 14.
  Real-time systems ofteninteract directly with hardware through specialized hardware interfaces.
• 15.
  Issues of safetyand reliability may may be the most important factors to be considered when designing the system.
• 16.
  Real-time systems areoften considered to be reactive systems. Given a stimulus, the system must produce a reaction or response within a specified time.
• 17.
  Periodic stimuli. Stimuliwhich occur at predictable time intervals A sensor may return a value every 250 milliseconds. The system response depends on that value.
• 18.
  Aperiodic stimuli. Stimuliwhich occur at unpredictable times For example, it is impossible to know when a power failure will occur.
• 19.
  A general modelof an embedded real- time system 04/12/2014 19
• 20.
  Real-time systems areusually organised as a number of parallel processes.
• 21.
  This allows themto respond in a timely way to events from the system’s environment.
• 22.
  It is difficultto design a sequential process in such a way that you can guarantee that predict the responsiveness of the system.
• 23.
  Sensor and actuatorprocesses 04/12/2014 23