Real-time operating systems are dedicated to some well-defined jobs which require very fast response time .The system must be fault –tolerant that is os must handle the error without going to unstable stage. The execution time is the most critical issue in real time so and they must finish the execution of the job within pre-defined time; boundary. The example of programs that run in real –time Os are: missile guiding system, medical monitoring system, flight simulation system etc. To finish the job after the dead line is as worse as not performing the job.
Online processing operating system is almost similar to real operating system but the result must be obtained in the presence of the user .The system for querying the bank balance in the account can be best example of online processing where result is obtained directly from the main database in the presence of the customer demanding information.
