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| Question | Answer |
| What are the five functions of an operating system? | - To provide and manage hardware resources (memory) - To provide an interface between the user and the machine - To provide and interface between hardware and software - To provide security for the data on the system - To provide utility software to maintain the system |
| What is an I/O interrupt? | Generated by an I/O device to signal that a job is complete or an error has occurred e.g. printer is out of paper |
| What is a timer interrupt? | generated by an internal clock indicating that the processor must attend to time critical activites |
| What is a hardware error interrupt? | E.g. power failure (this would have the highest priority of all interrupts) |
| What is a program interrupt? | Generated due to an error in a program, e.g. attempting to divide by 0 |
| What are the four types of interrupts? | I/O interrupt, timer interrupt, hardware error interrupt, program interrupt |
| What is a stack? | A place to store all the data from the CPU registers when a process is interrupted. This allows a task to resume from where it left off at a later time |
| What is scheduling used for? | To arrange processing jobs in an appropriate order based on priority |
| What are objectives of scheduling? | - To maximise the use of the computer - To be fair to all users - To provide a reasonable response time to all users - To prevent the system from failing if it was to become overloaded - To ensure that the system is consistent by always giving similar response times to similar activities from day to day |
| What can influence the order in which jobs are executed? | - The priority of the job - I/O or processor bound - The type of job e.g. batch processing or real time - Resource requirement e.g. the amount of time needed to complete a job, amount of memory needed - Resources used so far - How long the job has been waiting |
| What does I/O bound mean? | A job that makes little use of the processor, e.g. mostly input and output, small calculations |
| What does processor bound mean? | A job which heavily relies on the processor, e.g. continuously doing calculations with little input or output |
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