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Official PYQ · 1997Q3.6I/O SchedulingMCQ1 mark

GATE CS 1997 Q3.6 — I/O Scheduling

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The correct matching for the following pairs is:(A)Disk Scheduling(1)Round robin(B)Batch Processing(2)SCAN(C)Time-sharing(3)LIFO(D)Interrupt processing(4)FIFO\small \begin{array}{|cl|cl|}\hline \text{(A)} &\text{Disk Scheduling} & \text{(1)} &\text{Round robin} \\ \hline \text{(B)} &\text{Batch Processing} & \text{(2)} &\text{SCAN} \\ \hline \text{(C)} & \text{Time-sharing} & \text{(3)}&\text{LIFO} \\ \hline \text{(D)} &\text{Interrupt processing} & \text{(4)} &\text{FIFO} \\ \hline \end{array}

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Answer: C

To find the correct matching, let us analyze each pair:

  • (A) Disk Scheduling → (2) SCAN: SCAN (also known as the elevator algorithm) is a classic disk scheduling algorithm where the disk arm moves in one direction servicing requests until it reaches the end, then reverses direction.
  • (B) Batch Processing → (4) FIFO: In traditional batch processing systems, jobs are submitted in a queue and executed sequentially in the order of their arrival, which follows the First-In-First-Out (FIFO) policy.
  • (C) Time-sharing → (1) Round robin: Time-sharing systems allocate a small time slice (quantum) to each process in a cyclic manner to ensure interactive responsiveness. This is implemented using the Round Robin scheduling algorithm.
  • (D) Interrupt processing → (3) LIFO: When an interrupt occurs, the current CPU state (program counter, registers) is pushed onto a stack to be restored later. For nested interrupts, the last interrupted process is resumed first, which follows the Last-In-First-Out (LIFO) mechanism.

Thus, the correct matching is: A-2, B-4, C-1, D-3, which corresponds to Option C.

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