Q. What is the major difficulty that a programmer should overcome in writing an operating system for a real-time environment?

Answer: The major difficulty is keeping the operating system within the fixed time constraints of a real-time system. If the system doesn't complete a task in a certain time frame it may cause a breakdown of the entire system it is running. Thus when writing an operating system for a real-time system the writer should be sure that his scheduling schemes don't allow response time to exceed the time constraint.