In
computer science,
real-time computing (
RTC), or
reactive computing describes
hardware and
software systems subject to a "real-time constraint", for example operational deadlines from event to system response. Real-time programs must guarantee response within specified time constraints, often referred to as "deadlines". 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
guarantee a response within any timeframe, although
actual or
expected response times may be given.