Operating Systems | Scheduling Algorithms : LJF


Longest Job First

This algorithm schedules process with longest burst time. The scheduling can be either preemptive or non-preemptive.

Example: Find the completion time, turn around time, waiting time and response time of given set of processes in the following table?

  • Use Longest First Algorithm.
  • No preemption
  • No I/O request will be there from any process
  • Arrival time is relative to CPU on time
Process Number AT BT
1 0 3
2 1 3
3 2 4
4 2 1



Solution :

The time analytics of above processes can be depicted as shown below

By analyzing above representation completion time, turn around time and waiting time can be calculated as given below.

Process Number AT BT CT TAT WT
1 0 3 3 3 0
2 1 3 10 9 6
3 2 4 7 5 1
4 2 1 11 9 8

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