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GATE CSE Operating Systems — practice questions

Explore 19 free Operating Systems questions in GATE CSE Computer Science. Open each question or exercise to read its content, reference answers and available explanation.

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Operating Systems questions and exercises with answers

Showing questions 1–19 of 19.

The Process Control Block (PCB) storesRead the answer and worked solution →Launching Chrome twice on the same machine createsRead the answer and worked solution →A running process that issues a blocking disk read transitions to which state?Read the answer and worked solution →Two threads inside the same process shareRead the answer and worked solution →In the many-to-one user-to-kernel thread mapping, a single blocking I/O callRead the answer and worked solution →Three processes arrive at t=0 with bursts 24, 3, 3. The average waiting time under SJF isRead the answer and worked solution →Response time, the metric MLFQ optimises most for interactive workloads, isRead the answer and worked solution →The SHORTEST JOB FIRST (SJF) scheduler addresses the convoy effect byRead the answer and worked solution →The TURNAROUND TIME of a job is defined asRead the answer and worked solution →A scheduling DISCIPLINE (or policy) is BLIND if itRead the answer and worked solution →Jobs A (run time 100, arrival 0), B (run time 10, arrival 0), C (run time 10, arrival 0) under SJF give what average turnaround?Read the answer and worked solution →The PRIMARY DISADVANTAGE of FIFO scheduling isRead the answer and worked solution →Which of the following is NOT typically minimised by a CPU scheduler?Read the answer and worked solution →A LOCK (mutex) is used by concurrent threads toRead the answer and worked solution →A LOCK is considered FAIR ifRead the answer and worked solution →A CRITICAL SECTION isRead the answer and worked solution →Suppose thread A acquires lock L1, then thread B acquires lock L2. Now A tries to acquire L2 while B tries to acquire L1. What is this situation called?Read the answer and worked solution →A LIVELOCK differs from a DEADLOCK in thatRead the answer and worked solution →On a MULTI-CORE system, a SPIN LOCK is generallyRead the answer and worked solution →

Worked practice questions

The Process Control Block (PCB) stores

  1. runtime state: PID, registers, memory map, files
  2. only the program's compiled bytecode
  3. the OS kernel itself
  4. user passwords and authentication tokens
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Correct answer: A. runtime state: PID, registers, memory map, files

The PCB is the OS's per-process bookkeeping record. It holds everything needed to suspend and resume the process: PID, register values, program counter, memory layout, open file descriptors, scheduling priority, signals pending. Bytecode lives in memory pages, not the PCB the kernel itself is unrelated passwords belong to user/session management.

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Launching Chrome twice on the same machine creates

  1. one program and one process
  2. one program, two distinct processes with their own PCBs
  3. two programs but a shared process
  4. two processes that share the same heap and stack
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Correct answer: B. one program, two distinct processes with their own PCBs

Chrome is the program (the executable on disk). **Each launch is a separate process:** own PID, own memory map (stack, heap), own open file table, own PCB. They may share read-only code pages but never live data. The other options confuse process vs program or imagine shared mutable state across processes.

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A running process that issues a blocking disk read transitions to which state?

  1. Terminated state
  2. Ready (runnable)
  3. Waiting (Blocked)
  4. New (admitted)
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Correct answer: C. Waiting (Blocked)

When a process issues a blocking system call (e.g., a synchronous disk read), it cannot continue until the I/O completes. The OS moves it to the Waiting (Blocked) state and frees the CPU for another process. When the disk reports completion, the process transitions back to Ready, awaiting the scheduler. Terminated is for exit New is for admission Ready is the waiting-for-CPU state, not waiting-for-I/O.

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