# A scheduling algorithm assigns priority proportional to the waiting time of a process. Every process starts with priority zero (the lowest priority).

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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 everyT time units and decides the next process to schedule. Which one of the following is TRUE if theprocesses have no I/O operations and all arrive at time zero?
1. This algorithm is equivalent to the first-come-first-serve algorithm.
2. This algorithm is equivalent to the round-robin algorithm.
3. This algorithm is equivalent to the shortest-job-first algorithm.
4. This algorithm is equivalent to the shortest-remaining-time-first algorithm.

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Correct Answer - Option 2 : This algorithm is equivalent to the round-robin algorithm.

Concepts:

• First come first serve automatically executes queued requests and processes in order of their arrival.
•  Round robin: In RR, each ready task runs turn by turn only in a cyclic queue for a limited time slice.
• Shortest –job-first: In which the process having the smallest execution time present in ready queue is chosen for the next execution.
• Shortest-remaining-time-first: In this scheduling algorithm, the process with the smallest amount of time remaining until completion is selected to execute next.

Data:

The given scheduling algorithm assigns priority proportional to the waiting time of a process and every process starts with priority zero (the lowest priority). The scheduler re-evaluates the process priorities every T.

Explanation

With options elimination method

• The scheduler re-evaluates the process priorities every T time units and decides the next process to schedule means here the algorithm using- pre-emptive approach. By this analogy we can eliminate the option 1(FCFS) and 3(SJF).
• This means there must be a time quantum T exists without time quantum scheduler cannot re-evaluates the process priorities and the scheduling algorithm assigns priority proportional to the waiting time of a process instead the less service time.
• From this it is quite clear that the algorithm cannot be Shortest-remaining-time-first and it will equivalent to Round-robin algorithms.