Operating System Interview Question and Answers

31. Why thread is called as a lightweight process?
  It is called light weight process to emphasize the fact that a thread is like a process but is more efficient and uses fewer resources( n hence “lighter”)and they also share the address space.
32. What are operating system services?
 
  • Program execution
  • I/O operations
  • File system manipulation
  • Communication
  • Error detection
  • Resource allocation
  • Accounting
  • Protection
33. What is a process?
 
  • A program in execution is called a process. Or it may also be called a unit of work.
  • A process needs some system resources as CPU time, memory, files, and i/o devices to accomplish the task.
  • Each process is represented in the operating system by a process control block or task control block (PCB).
    Processes are of two types
  • Operating system processes
  • User processes
34. What are the different job scheduling in operating systems?
 
  • Scheduling is the activity of the deciding when process will receive the resources they request.
  • FCFS ---> FCSFS stands for First Come First Served. In FCFS the job that has been waiting the longest is served next.
  • Round Robin Scheduling--->Round Robin scheduling is a scheduling method where each process gets a small quantity of time to run and then it is preempted and the next process gets to run. This is called time-sharing and gives the effect of all the processes running at the same time.
  • Shortest Job First ---> The Shortest job First scheduling algorithm is a nonpreemptive scheduling algorithm that chooses the job that will execute the shortest amount of time.
  • Priority Scheduling--->Priority scheduling is a scheduling method where at all times the highest priority process is assigned the resource.
35. What is dual-mode operation?
  In order to protect the operating systems and the system programs from the malfunctioning programs the two mode operations were evolved
  • System mode
  • User mode
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