C++ Program of SSTF (Short seek time first )Disk scheduling Algorithms in operating system (OS).

   What is SSTF disk scheduling:-

                                                        Shortest seek time first (SSTF) algorithm selects the disk I/O request which requires the least disk arm movement from its current position regardless of the direction. It reduces the total seek time as compared to FCFS.

Example:-: Given the following queue -- 95, 180, 34, 119, 11, 123, 62, 64 with the Read-write head initially at the track 50 and the tail track being at 199.

Advantage:-

1. seek time reduces as compared to the FCFS
2. Less waiting time and response time 
3. Increase throughput.

Disadvantage:-

1. starvation occurred

  C++      C      Python  

#include<bits/stdc++.h>

using namespace std;

int main()

{

    int RQ[100],i,n,TotalHeadMoment=0,initial,count=0;

    cout<<"Enter the number of Requests\n";

    cin>>n;

    cout<<"Enter the Requests sequence\n";

    for(i=0;i<n;i++)

     cin>>RQ[i];

    cout<<"Enter initial head position\n";

    cin>>initial;

   

    // logic for sstf disk scheduling

   

        /* loop will execute until all process is completed*/

    while(count!=n)

    {

        int min=INT_MAX,d,index;

        for(i=0;i<n;i++)

        {

           d=abs(RQ[i]-initial);

           if(min>d)

           {

               min=d;

               index=i;

           }

           

        }

        TotalHeadMoment=TotalHeadMoment+min;

        initial=RQ[index];

       

        RQ[index]=INT_MAX;

        count++;

    }

   

    cout<<"Total head movement is "<<TotalHeadMoment;

    return 0;

}

Output:-

Enter the number of Request

8

Enter Request Sequence

95 180 34 119 11 123 62 64

Enter initial head Position

50

Total head movement is 236

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•   Program of disk scheduling algorithm

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