Real Time Operating Systems

U

System must respond to external stimuli within a finite and specified time.

Correctness depends not only on logical result BUT also on response time.

Problem : Shedule all activities to meet some requirements.

Hard Real Time : Absolutely imperative that responses occur within specified deadlines. Late result failure.

Soft Real Time : Response times are important, but system will still function if deadlines are missed.

Embedded System : Systems which are interfaced to some external physical equipment, and perform monitoring and control.
The computer is PART of the overall system, and hence Real Time.

Real Time systems are used for :
Hard : Nuclear Power Stations, Flight Control, Missile Guidance
Soft : Train or Airline Reservation
Embedded : Washing Machine, Chemical plant control etc

Distinction between OS and R/T systems are quite blurred