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CPU and I/O Scheduling

GATE CSE 2013 · Q10

MCQ1 markMedium

Time

A scheduling algorithm assigns priority proportional to the waiting time of a process. Every process starts with priority zero (the lowest priority). The scheduler re-evaluates the process priorities every TT time units and decides the next process to schedule. Which one of the following is TRUE if the processes have no I/O operations and all arrive at time zero?

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Solution

Step-by-step verified solution

Official answer: B) This algorithm is equivalent to the round-robin algorithm.

CPU and I/O Scheduling

Consider the execution flow:

  1. All processes arrive at time t=0t = 0 with an initial priority of 00.

  2. The scheduler selects a process to run for a time slice of TT units.

  3. During these TT units, the running process accumulates no additional waiting time, whereas all non-running (waiting) processes have their waiting time increased by TT, thus increasing their priority.

  4. At t=Tt = T, the scheduler picks the process with the highest priority (the one that has waited the longest).

  5. This process then runs for TT units, while the others accumulate more wait time. After every process has executed once for TT units, the cycle repeats in the same order.

This behavior is identical to the Round-Robin scheduling algorithm with a time quantum of TT.

Hence, option (B) is correct.

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This CPU and I/O Scheduling previous year question is Q10 of the GATE CSE 2013 paper. Find more GATE CSE PYQs on CPU and I/O Scheduling in Operating Systems, or browse all GATE CSE PYQs.

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CPU and I/O Scheduling in GATE CSE

CPU and I/O Scheduling has 25 GATE CSE PYQs across 22 papers from 2011 to 2026. 4 of them are 1-mark MCQs like this one, and it is the only one in GATE CSE 2013.

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GateAI solution cardGATE CSE 2013 · Q10 · MCQ

A scheduling algorithm assigns priority proportional to the waiting time of a process. Every process starts with priority zero (the lowest priority). The scheduler re-evaluates the process priorities every T time units and decides the next process to schedule. Which one of the following is TRUE if the processes have no I/O operations and all arrive at time zero?

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Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.