OS Priority C Program

Operating Systems Lab Manual / OS Priority C Program

Program Name	Write a C Program for CPU scheduling algorithm Priority.
Theory	In Priority CPU scheduling algorithm the process whose Priority is more will be served first by the processor. The processor gets processes from the ready Queue. Waiting time (n) = waiting time (n-1) + Burst time (n-1) Turnaround time (n)= waiting time(n)+Burst time(n) Average waiting time = Total waiting Time / Number of process. Average Turnaround time = Total Turnaround Time / Number of process.
Program	#include<stdio.h> main() { int process[20],bt[20],priorities[20], wt[20],tat[20],i, k, n, temp; float wtavg, tatavg; printf("Enter number of processes : "); scanf("%d",&n); for(i=0;i<n;i++) { process[i] = i; printf("Enter Burst Time & Priority of Process %d : ",i); scanf("%d%d",&bt[i], &priorities[i]); } for(i=0;i<n;i++) for(k=i+1;k<n;k++) if(priorities[i] > priorities[k]) { temp=process[i]; process[i]=process[k]; process[k]=temp; temp=bt[i]; bt[i]=bt[k]; bt[k]=temp; temp=priorities[i]; priorities[i]=priorities[k]; priorities[k]=temp; } wtavg = wt[0] = 0; tatavg = tat[0] = bt[0]; for(i=1;i<n;i++) { wt[i] = wt[i-1] + bt[i-1]; tat[i] = tat[i-1] + bt[i]; wtavg = wtavg + wt[i]; tatavg = tatavg + tat[i]; } printf("\n Process \t\t Priority \t Burst Time \t Waiting Time \t Turn Around Time "); for(i=0;i<n;i++) printf("\n%d \t\t %d \t\t %d \t\t %d \t\t %d ",process[i],priorities[i],bt[i],wt[i],tat[i]); printf("\nAverage Waiting Time : %f : ",wtavg/n); printf("\nAverage Turnaround Time : %f ",tatavg/n); }
Input	Enter number of processes : 5 Enter Burst Time & Priority of Process 0 : 9 3 Enter Burst Time & Priority of Process 1 : 1 1 Enter Burst Time & Priority of Process 2 : 2 5 Enter Burst Time & Priority of Process 3 : 1 6 Enter Burst Time & Priority of Process 4 : 4 2
Output	Process Priority Burst Time Waiting Time Turn Around Time 1 1 1 0 1 4 2 4 1 5 0 3 9 5 14 2 5 2 14 16 3 6 1 16 17 Average Waiting Time: 7.200000 Average Turnaround Time: 10.600000

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