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Real-time computing
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<p>Real-time computing (RTC) is the <a href="/facts/Computer_science/lN3pEyPz">computer science</a> term for <a href="/facts/Computer_hardware/8jSjsCNv">hardware</a> and <a href="/facts/Software/RP79lVSW">software</a> systems subject to a "real-time constraint", for example from <a href="/facts/Event_(synchronization_primitive)/y5RyqEAW">event</a> to <a href="/facts/Event_(computing)/0YdM6AoB">system response</a>. Real-time programs must guarantee response within specified time constraints, often referred to as "deadlines". </p><p>The term "real-time" is also used in <a href="/facts/Computer_simulation/Re6o8vzN">simulation</a> to mean that the simulation's clock runs at the same speed as a real clock. </p><p>Real-time responses are often understood to be in the order of milliseconds, and sometimes microseconds. A system not specified as operating in real time cannot usually <i>guarantee</i> a response within any timeframe, although <i>typical</i> or <i>expected</i> response times may be given. Real-time processing <i>fails</i> if not completed within a specified deadline relative to an event; deadlines must always be met, regardless of <a href="/facts/Load_(computing)/J2v5XarQ">system load</a>. </p><p>A real-time system has been described as one which "controls an environment by receiving data, processing them, and returning the results sufficiently quickly to affect the environment at that time". The term "real-time" is used in <a href="/facts/Industrial_control_system/YzgsMy2x">process control</a> and <a href="/facts/Enterprise_system/RGa1b0bC">enterprise systems</a> to mean "without significant delay". </p><p>Real-time software may use one or more of the following: <a href="/facts/Synchronous_programming_language/T8CFYfyG">synchronous programming languages</a>, <a href="/facts/Real-time_operating_system/IvUCFwCL">real-time operating systems</a> (RTOSes), and real-time networks. Each of these provide essential frameworks on which to build a real-time software application. </p><p>Systems used for many <a href="/facts/Safety-critical_system/vhVc7NJU">safety-critical</a> applications must be real-time, such as for control of <a href="/facts/Fly-by-wire/nhyXB248">fly-by-wire</a> aircraft, or <a href="/facts/Anti-lock_brakes/SmXvJn6G">anti-lock brakes</a>, both of which demand immediate and accurate mechanical response. </p>