C++ Program For C-LOOK Disk Scheduling Algorithm | C++ Programming

C-LOOK Disk Scheduling Algorithm-

• Circular-LOOK Algorithm is an improved version of the LOOK Algorithm.
• Head starts from the first request at one end of the disk and moves towards the last request at  the other end servicing all the requests in between.
• After reaching the last request at the other end, head reverses its direction.
• It then returns to the first request at the starting end without servicing any request in between.
• The same process repeats.

Advantages-

• It does not causes the head to move till the ends of the disk when there are no requests to be serviced.
• It reduces the waiting time for the cylinders just visited by the head.
• It provides better performance as compared to LOOK Algorithm.
• It does not lead to starvation.
• It provides low variance in response time and waiting time.

Disadvantages-

• There is an overhead of finding the end requests.

C++ program for C-LOOK Disk Scheduling Algorithm

#include <iostream>
#include <stdlib.h>
using namespace std;
class clook_disk
{
    int ref[100];
    int ttrk, cur, size, prev;
    int sort();
public:
    void getdata();
    void total_move();
};
int clook_disk::sort()
{
    int temp;
    for (int i = 0; i < size - 1; i++)
        for (int y = 0; y < size - 1; y++)
            if (ref[y] > ref[y + 1])
            {
                temp = ref[y];
                ref[y] = ref[y + 1];
                ref[y + 1] = temp;
            }
    for (int i = 0; i < size; i++)
        if (ref[i] > cur)
            return i;
    return size;
}
void clook_disk::getdata()
{
    cout << "Enter total number of tracks : ";
    cin >> ttrk;
    ttrk--;
    cout << "Enter the current position of head : ";
    cin >> cur;
    cout << "Enter previous position of head : ";
    cin >> prev;
    cout << "Enter the size of queue : ";
    cin >> size;
    cout << "Enter the request for tracks : ";
    for (int i = 0; i < size; i++)
        cin >> ref[i];
}
void clook_disk::total_move()
{
    int num = cur, move = 0, ind, dir = cur - prev;
    ind = sort();
    if (dir > 0)
    {
        for (int i = ind; i < size; i++)
        {
            move += ref[i] - num;
            num = ref[i];
        }
        if (ind != 0)
        {
            num = ref[0];
            cout << move << " ";
            for (int i = 0; i <= ind - 1; i++)
            {
                move += ref[i] - num;
                num = ref[i];
            }
        }
    }
    else
    {
        for (int i = ind - 1; i >= 0; i--)
        {
            move += num - ref[i];
            num = ref[i];
        }
        num = ref[size - 1];
        for (int i = size - 2; i >= ind; i--)
        {
            move += num - ref[i];
            num = ref[i];
        }
    }
    cout << "Total head movements : " << move;
}
int main()
{
    clook_disk clook;
    clook.getdata();
    clook.total_move();
    return 0;
}

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