Scheduling algoritmy are essential in operating systems to management process execution accessficiently. They determe the order in which processes are allocated CPU time, impacting systeme performance and responveness. This article compares three common algoritms: First- Come, First- Servek (FCFS), Shortett Job First (SJF), and Round Robin, with calculations to ilustrate their diferences.

First- Come, First- Served (FCFS)

FCFS schedules processes in then thee order they arrive. It is simple but can lead to long waiting times for shorter processes, known as thee commercite; convoy effect. cottage;

Example: Processes with burst times 5, 3, and 8 arrive sequentially. The Gantt chart shows execution order and calculations for waiting and turnaround times.

Výpočty:

  • Process 1: Waiting Time = 0, Turnaround Time = 5
  • Process 2: Waiting Time = 5, Turnaround Time = 8
  • Process 3: Waiting Time = 8, Turnaround Time = 16

Shortett Jobe First (SJF)

SJF selekts the process with the smallett burtt time next. It minimizes average waiting time but implicans knowdge of process durations forehand.

Using thee same processes, SJF schedules them am a 3, 5, then 8 units, lealing to different waiting times.

Výpočty:

  • Process 2: Waiting Time = 0, Turnaround Time = 3
  • Process 1: Waiting Time = 3, Turnaround Time = 8
  • Process 3: Waiting Time = 8, Turnaround Time = 16

Round Robin Scheduling

Round Robin assigns each process a figed time sque or quantum. Processes are cycled courgh until completion, promoting fairness and responveness.

Předpoklad a quantum of 2 units, thee processes are scheduled in cycles, and calculations are based on total execution time and waiting periods.

Example calculations for process completion times and waiting times are as follows:

  • Process 1: Waiting Time = 4, Turnaround Time = 9
  • Process 2: Waiting Time = 2, Turnaround Time = 5
  • Process 3: Waiting Time = 8, Turnaround Time = 16