Simplify the following text for a Grade 7 native English-speaking person.
Original: In computer science , real-time computing ( RTC ) , or reactive computing , is the study of hardware and software systems that are subject to a `` real-time constraint '' â '' i.e. , operational deadlines from event to system response .
Simplified: Real-time computing is a field of Computer science . The idea is to design systems that have a real-time constraint .