A real-time system has well-defined, fixed time constraints. Processing
must be done within the defined constraints, or the system will fail. For
instance, it would not do for a robot arm to be instructed to halt after it had
smashed into the car it was building. A real-time system functions correctly
only if it returns the correct result within its time constraints. Contrast this
system with a time-sharing system, where it is desirable (but not mandatory)
to respond quickly, or a batch system, which may have no time constraints at
all.