What is a real time device?

Answer 1

Real time is the current time and real time devices are suppose to always keep the correct time no matter what. In hardware design, this is typically accomplished by using a real time clock chip (RTC), which typically uses its own crystal and battery (or some other form of uninterrupted power supply), as opposed to deriving the current time using a software emulation implemented on the main processor.

Real time has another meaning in context with software design. In software design, real time generally means the ability of software to respond very quickly and with deterministic latency to certain events, typically external events based on the sampling of input circuitry, or events not generated based on the executing software itself, such as events produced by timer or counter circuitry. For example, a real-time computer controlling the ignition process of an internal combustion engine must trigger the ignition spark for each cylinder at the exact right moment and with very high accuracy and precision in order to optimize the burning of the fuel. This use of the term real time is much disputed, though, as there is no clear definition of the response times, accuracy and precision required to qualify for the term real time system.