Data is received processed and results are given so fast that the process seems instantaneous to the user. Such a system is named as real time system.
In real life situations, we come across many systems where it is not sufficient that correct results are produced, but such results must be produced within a specified time frame (deadline).
Note: A real-time system must satisfy the requirement of producing the desired result before a certain deadline. If it delivers the correct result, but after the deadline, the system is regarded as having failed. Thus, in a real-time system timely production of result is as important as its correct execution capability.
Real-time systems provide immediate processing and also respond to user’s commands immediately. Some examples of real-time systems are the following:
a) Airplane control and space vehicle operations: Failure to process accelerometer data within a certain period (say every 20×10-3 sec)can cause the aircraft to deviate from its right course or may even cause it to crash.
b) Nuclear thermal power plant: Failure to respond in time to an error condition in a nuclear thermal power plant system could result in a melt-down.
c) Automated factory: Failure to respond in time to an error condition in the assembly line of an automated factory could result in the production of several defective products which have to be discarded finally.
d) Equity sales/ purchase on National Stock Exchange: Buyers purchasing and selling equities on the National Stock Exchange is carried out as a real time system because they see the price of equities from moment to moment.