Operating Systems Flashcards
What is software?
A collection of electronically stored instructions that allows one to interact with a computer
What are the 2 types of software?
- Application software
- System software
True or False
System software lies between application software and hardware
True
Operating Systems have 3 rows, which are what?
- Process management
- Memory management
- Device management
What is process management?
manages numerous concurrently running programs
What can cause a process to move to the waiting stage?
When there is not enough data
What is the process for instructions to be completed?
- New
- Operating systems copy program code into RAM
*ADMITTED
- Ready
- another process may be running
*Dispatch
- Running
- CPU is executing the instructions
*EXIT
- Terminated
- Memory and other resources are freed
What is CPU Scheduling?
The act of determining which process in the ready state should be moved to the running state
Which process gets to move from the ready state to the running state first?
- First-come, First-served
- Shortest Job Next
- Round Robin
What are the 2 kinds of scheduling rules?
- Non-preemptive scheduling
- Preemptive scheduling
What is Non-preemptive scheduling?
Once you go into the running stage, you are guaranteed to finish the process
What is Preemptive scheduling?
Sometimes, when we are being served, we get interrupted by another process
What is a turn-around time?
The amount of time between when a process arrives in the ready state for the first time and when it exits the running state for the last time
- total time for the process to be executed
What is service time?
The time needed for each is listed in this table
How does First-come first first-served work?
The first ordering structure that comes in is the first processed
Is first-come, first-served non-preemptive or preemptive?
non-preemptive
How does Shortest Job Next work?
looks at all the processes in the ready state and dispatches the one with the shortest service time
Is Shorest Job Next preemptive or preemptive?
non-preemptive
What is a problem that can arise while using the Shortest Job Next?
The service time may not always be known ahead of time
True or False
Shortest Job Next is a provably optimal strategy for average turn-around time
True
How does Round Robin work?
distributes an equal processing time for each process and will establish time slices for each until each process is completed
Is Round Robin non-preemptive or preemptive?
preemptive
Which of the CPU scheduling algorithms is the most fair?
Round Robin
