Real time computing is where a computer can act guaranteed within a specified time frame.
Real time computing is where a computer can act guaranteed within a specified time frame. For RTC being fast enough in 99% of all cases is not good enough. Real time computing means no deadlines may be missed, which means knowing precisely how long some operations take and scheduling them in such a way that deadline are always made.
This conflicts with things like automatic garbage collection which can trigger outside the users control and thus cause a missed deadline. Real, hard real time systems are hard.