System software notes
10cs52(vtuplanet.com), Lecture
notes of System Programming
A distributed OS provides better _______ by...? - ANSProvides better service:
- Faster processing
- If one section fails, others can potentially continue operating
- Reduction in delays
A software development company is building an operating system for a mobile phone that is in the
process of being designed.
One of the developers is responsible for writing the code for what happens when the CPU receives an
interrupt. Outline what the code must do. [6] - ANS- Complete the current FDE Cycle
- Check the priority of the incoming interrupt.
- If it's of a higher priority than the current task, contents of PC/memory stored in memory in a stack
- The relevant interrupt service routine is loaded by loading the relevant value into the program counter.
- When the interrupt service routine is complete the previous state is popped from the stack
- And are loaded back into the registers
An operating system uses scheduling. One method of scheduling is first come, first served.
i) Explain why the first come, first served scheduling method may not be efficient. [2]
ii) Describe one other scheduling method [2]
iii) Explain why scheduling is necessary [4] - ANSSome instructions may take less time than the ones at
the front, which may take a while, meaning instructions that can be done in seconds and held up by ones
that take longer
Shortest Remaining Time - the task that takes the least amount of time required to complete the job is
done first
Scheduling allows for processes to be ordered in a way that is beneficial. It ensures efficiency and
fairness between parties using the program. Maximise number of interactive users.
Benefits of virtual machine? - ANSEnergy consumption reduction
More control over network and users
Easy to move file of virtual machine
Compare and contrast the functions of operating systems designed for a personal computer and a
satellite navigation system in a car [7] - ANSA personal computer is likely to be a multi-task operating
system or a general purpose operating system, whereas a satellite navigation system in a car is likely to
be an embedded system.
A multi-task operating system allows multiple tasks to be seemingly carried out at once, but the operating
system just rapidly switches between the tasks. In contrast, an embedded system is built for limited,
specific functions, based on what is required.
