Process Scheduling

Question 1

Name the four types of scheduling

Answer 1

Long term
Medium Term
Short Term
I/O

Question 2

What is long term scheduling?

Answer 2

The decision to add to the pool of processes to be executed

Question 3

What is medium term scheduling?

Answer 3

The decision to add to the number of processes that are partially or fully in main memory

Question 4

What is short term scheduling?

Answer 4

The decision as to which available process will be executed by the processor

Question 5

What is I/O scheduling?

Answer 5

The decision as to which process’s pending I/O request shall be handled by an available I/O device

Question 6

Name the two types of queues

Answer 6

Job Queue and Ready Queue

Question 7

What is the job queue?

Answer 7

a list of all the processes or jobs that are waiting to be executed. These processes are typically in a “new” or “created” state.

Question 8

What is the ready queue?

Answer 8

The processes that are residing in main memory and are ready and waiting to be executed are kept in a list called a ready queue.

Question 9

What is the difference between preemptive and non-preemptive scheduling?

Answer 9

Preemptive scheduling allows the operating system to interrupt and switch between processes at any time.
Non-preemptive scheduling only allows processes to be switched voluntarily by the process itself.
Preemptive is more responsive, while non-preemptive is simpler but less responsive.

Question 10

What are i/o bound processes?

Answer 10

spends more time doing I/O than computations, many short CPU bursts

Question 11

What are CPU bound processes?

Answer 11

spends more time doing computations; few very long CPU bursts

Question 12

What is the effect of swapping on OS Overhead?

Answer 12

The OS needs to maintain and manage the swapping process, which includes keeping track of the status and location of swapped-out programs, deciding which programs to swap in or out, and performing the actual data transfer operations. This management requires CPU cycles and resources.

Question 13

List five (5) performance criteria that can be used for selecting or comparing CPU scheduling algorithm.

Answer 13

1. CPU Utilization: measures the extent to which the CPU is kept busy processing tasks.
2. Throughput: refers to the number of processes completed per unit of time.
3. Turnaround Time: total time taken from the submission of a process to its completion.
4. Waiting time: measures the total time a process spends waiting in the ready queue before it is executed.
5. Response time: time taken from when a request is made until the first response is produced.