Operating System ( Lab Code.c )

FCFS.c

#include<stdio.h>
#include<process.h>
int main()
{
    char p[10][5];
    int tot=0,wt[10], pt[10], i,n;
    double avg=0;

    printf("enter no of processes: ");
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        printf("enter process%d name: ",i+1);
        scanf("%s",&p[i]);
        printf("enter process time :");
        scanf("%d",&pt[i]);
    }

    wt[0]=0;
    for(i=1;i<n;i++)
    {
        wt[i]=wt[i-1]+pt[i-1];
        tot=tot+wt[i];
    }
    avg=(double)tot/n;
    printf("p_name\t P_time\t w_time\n");
    for(i=0;i<n;i++)
        printf("%s\t%d\t%d\n",p[i],pt[i],wt[i]);
    printf("total waiting time=%d\n avg waiting time=%lf",tot,avg);

}

Priority Scheduling.c

#include<stdio.h>

int main()
{
    int bt[20],p[20],wt[20],tat[20],pr[20],i,j,n,total=0,pos,temp,avg_wt,avg_tat;
    printf("Enter Total Number of Process: ");
    scanf("%d",&n);

    printf("\nEnter Burst Time and Priority\n");
    for(i=0;i<n;i++)
    {
        printf("\nP[%d]\n",i+1);
        printf("Burst Time: ");
        scanf("%d",&bt[i]);
        printf("Priority: ");
        scanf("%d",&pr[i]);
        p[i]=i+1;
    }
    for(i=0;i<n;i++)
    {
        pos=i;
        for(j=i+1;j<n;j++)
        {
            if(pr[j]<pr[pos])
                pos=j;
        }

        temp=pr[i];
        pr[i]=pr[pos];
        pr[pos]=temp;

        temp=bt[i];
        bt[i]=bt[pos];
        bt[pos]=temp;

        temp=p[i];
        p[i]=p[pos];
        p[pos]=temp;
    }

    wt[0]=0;
    for(i=1;i<n;i++)
    {
        wt[i]=0;
        for(j=0;j<i;j++)
            wt[i]+=bt[j];

        total+=wt[i];
    }

    avg_wt=total/n;
    total=0;

    printf("\nProcess\t    Burst Time    \tWaiting Time\tTurnaround Time");
    for(i=0;i<n;i++)
    {
        tat[i]=bt[i]+wt[i];
        total+=tat[i];
        printf("\nP[%d]\t\t  %d\t\t    %d\t\t\t%d",p[i],bt[i],wt[i],tat[i]);
    }

    avg_tat=total/n;
    printf("\n\nAverage Waiting Time = %d",avg_wt);
    printf("\nAverage Turnaround Time = %d\n",avg_tat);

    return 0;
}

Round Robin.c

#include<stdio.h>

int main()
{

  int i,j,n,time,remain,flag=0,time_quantum;
  int wait_time=0,turnaround_time=0,arr[10],bt[10],rt[10];
  printf("Enter Total Process:\t ");
  scanf("%d",&n);
  remain=n;
  for(i=0;i<n;i++)
  {
    printf("Enter Arrival Time and Burst Time for Process Number %d :",i+1);
    scanf("%d",&arr[i]);
    scanf("%d",&bt[i]);
    rt[i]=bt[i];
  }
  printf("Enter Time Quantum:\t");
  scanf("%d",&time_quantum);
  printf("\n\nProcess\t|Turnaround Time|Waiting Time\n\n");
  for(time=0,i=0;remain!=0;)
  {
    if(rt[i]<=time_quantum && rt[i]>0)
    {
      time+=rt[i];
      rt[i]=0;
      flag=1;
    }
    else if(rt[i]>0)
    {
      rt[i]-=time_quantum;
      time+=time_quantum;
    }
    if(rt[i]==0 && flag==1)
    {
      remain--;
      printf("P[%d]\t|\t%d\t|\t%d\n",i+1,time-arr[i],time-arr[i]-bt[i]);
      wait_time+=time-arr[i]-bt[i];
      turnaround_time+=time-arr[i];
      flag=0;
    }
    if(i==n-1)
      i=0;
    else if(arr[i+1]<=time)
      i++;
    else
      i=0;
  }
  printf("\nAverage Waiting Time= %f\n",wait_time*1.0/n);
  printf("Avg Turnaround Time = %f",turnaround_time*1.0/n);

  return 0;
}

SJF.c

#include<stdio.h>

int main()
{
    int bt[20],p[20],wt[20],tat[20],i,j,n,total=0,pos,temp;
    double avg_wt,avg_tat;
    printf("Enter number of process: ");
    scanf("%d",&n);

    printf("\nEnter Burst Time:\n");
    for(i=0;i<n;i++)
    {
        printf("p%d: ",i+1);
        scanf("%d",&bt[i]);
        p[i]=i+1;
    }

    for(i=0;i<n;i++)
    {
        pos=i;
        for(j=i+1;j<n;j++)
        {
            if(bt[j]<bt[pos])
                pos=j;
        }

        temp=bt[i];
        bt[i]=bt[pos];
        bt[pos]=temp;

        temp=p[i];
        p[i]=p[pos];
        p[pos]=temp;
    }

    wt[0]=0;
    for(i=1;i<n;i++)
    {
        wt[i]=0;
        for(j=0;j<i;j++)
            wt[i]+=bt[j];

        total+=wt[i];
    }

    avg_wt=(double)total/n;
    total=0;

    printf("\nProcess\t    Burst Time    \tWaiting Time\tTurnaround Time");
    for(i=0;i<n;i++)
    {
        tat[i]=bt[i]+wt[i];
        total+=tat[i];
        printf("\np%d\t\t  %d\t\t    %d\t\t\t%d",p[i],bt[i],wt[i],tat[i]);
    }

    avg_tat=(double)total/n;
    printf("\n\nAverage Waiting Time = %lf",avg_wt);
    printf("\nAverage Turnaround Time = %lf\n",avg_tat);
}