Podcast
Questions and Answers
What is a program called when its instructions are being executed by a CPU?
What is a program called when its instructions are being executed by a CPU?
- Algorithm
- Operation
- Process (correct)
- Task
Why does the operating system need to manage processes and resources efficiently?
Why does the operating system need to manage processes and resources efficiently?
- To slow down the computer
- To prevent inconsistency and deadlock (correct)
- To reduce the number of available resources
- To increase power consumption
What is the main reason why some resources need to be executed by only one process at a time?
What is the main reason why some resources need to be executed by only one process at a time?
- To speed up the system
- To overload the CPU
- To ensure consistency and prevent deadlock (correct)
- To allow multiple processes to access the resource simultaneously
In the context of the operating system, what term is heavily favored over 'job' for a program in execution?
In the context of the operating system, what term is heavily favored over 'job' for a program in execution?
Why might multiple processes in a system require the same resource simultaneously?
Why might multiple processes in a system require the same resource simultaneously?
What scheduling algorithm gives the minimum average waiting time for a set of processes?
What scheduling algorithm gives the minimum average waiting time for a set of processes?
In SJF scheduling, what does the priority represent?
In SJF scheduling, what does the priority represent?
What is the characteristic of Round Robin Scheduling?
What is the characteristic of Round Robin Scheduling?
Which scheduling algorithm is designed for interactive systems?
Which scheduling algorithm is designed for interactive systems?
What defines the order of execution in Priority based scheduling?
What defines the order of execution in Priority based scheduling?
Which scheduling algorithm involves a cyclic execution of processes?
Which scheduling algorithm involves a cyclic execution of processes?
What happens to a process in Round Robin Scheduling if it doesn't complete its execution during the assigned time quantum?
What happens to a process in Round Robin Scheduling if it doesn't complete its execution during the assigned time quantum?
What type of systems is Round Robin Scheduling specifically designed for?
What type of systems is Round Robin Scheduling specifically designed for?
Which scheduling algorithm allocates the CPU to the process with the highest priority?
Which scheduling algorithm allocates the CPU to the process with the highest priority?
What does SJF stand for in Shortest-Job-First Scheduling?
What does SJF stand for in Shortest-Job-First Scheduling?
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Study Notes
Selection Process in Scheduling
- Carried out by appropriate schedulers to manage job execution in a system.
Types of Schedulers
-
Short Term Scheduler (CPU Scheduler):
- Selects jobs from the ready queue and dispatches them to the CPU for execution.
- Utilizes scheduling algorithms to choose the next job.
- Critical role; a job with high CPU burst time can cause delays for subsequent jobs.
-
Medium Term Scheduler:
- Manages swapped out processes and changes states between running and waiting.
- Removes processes from running state to accommodate other processes, facilitating swapping.
- Responsible for suspending (temporarily halting) and resuming processes.
Process Timing Definitions
- Arrival Time: The moment a process enters the ready queue.
- Burst Time: Total CPU time required for a process's completion, excluding waiting time.
- When an I/O operation is requested, the short term scheduler saves the process context and transitions it from running to waiting.
Scheduling Algorithms
-
First-Come, First-Serve (FCFS):
- Simplest scheduling algorithm.
- Processes are executed in the order of their arrival time.
- Non-preemptive scheduling where a running process cannot be interrupted.
- Characteristics:
- Maximum CPU utilization.
- Fair CPU allocation.
- High throughput.
- Lower turnaround time, waiting time, and response time.
-
Shortest-Job-First (SJF) Scheduling:
- Each process is assigned the length of its next CPU burst for scheduling.
- Two variants:
- Non-Preemptive: Once a process is allocated CPU, it runs to completion.
- Preemptive: A new process with a shorter CPU burst can interrupt the currently running process.
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