As fast as required. A real-time system must respond to a signal, event or request fast enough to satisfy some requirement. Real time often refers to process control and embedded systems. For example, space flight computers must respond to changing conditions in order to keep the rocket ship on course. Industrial robots must respond quickly in order to keep the assembly line moving at full speed. Antilock brakes and other driving assist systems must respond to changing road conditions immediately in order to benefit the driver and vehicle. See embedded system
, real-time audio
, real-time video
and real-time search
Videoconferencing requires real-time systems that transmit video across the network and display it at the other end as quickly as the camera is capturing it. Gaming is another real-time application. The system must render video frames in immediate response to the user's inputs.
Business Systems - Not Really
The typical transaction processing system is not considered real time even though it often updates databases immediately. However, in the past, as business information systems became fast enough to respond to queries and updates in only a second or two, they were called real-time systems.
A Synonym for Now
Real time is increasingly used as a synonym for just plain "now." Real time implies an immediate response to an action. For example, "the test results are answered in real time" is correct usage meaning that the results come back immediately. However, "let's do the test in real time" as a way of saying "let's do it now," was not why the term was coined. See online