Write a program that implements the following disk-scheduling algorithms: (pick three)

a. fcfs
b. sstf
c. scan
d. c-scan
e, look
f. c-look

your program will service a disk with 5,000 cylinders numbered 0 to 4,999. the program will generate a random series of 50 requests and service them according to each of the algorithms you chose. the program will be passed the initial position of the disk head as a parameter on the command line and report the total amount of head movement required for each algorithm.

Explanation:

#include <stdio.h>

#include <stdlib.h>

#define CYLINDERS 5000

#define REQUESTS 1000

int initialHead = 0;

int disk[REQUESTS];

int* sortDisk()

{

  int temp = 0, m = 0, n = 0;

  //sort the disk using sorting algorithm

  for (m = 0; m < REQUESTS; ++m)

  {

      for (n = m + 1; n < REQUESTS; ++n)

      {

          if (disk[m] > disk[n])

          {

              temp = disk[m];

              disk[m] = disk[n];

              disk[n] = temp;

          }

      }

  }

  return disk;

}

int discSchedAlgFCFS(int *ran_array)

{

  int i = 0, headMovement = 0;

  int this_start = disk[initialHead];

  for (i = initialHead; i < REQUESTS; i++)

      //add absolute difference disk[i]

      //and this_start to head movement

      headMovement += abs(disk[i] - this_start);

  for (i = 0; i < initialHead; i++)

      headMovement += abs(this_start - ran_array[i]);

  //return head movments of fcfs

  return headMovement;

}

int discSchedAlgSSTF(int * disk)

{

  //befor start SSTF algorithm, first sort the disk

  disk = sortDisk();

  //Decalre the variables

  int s = initialHead - 1, l = initialHead + 1;

  int smallDiff = 0, largeDiff = 0;

  int headMovement = 0, n = REQUESTS - 2;

  int new_head = initialHead, head_value = disk[initialHead];

  //loop until the total number of request n to reach 0

  while (n >= 0)

  {

      //absolute difference disk[new_head]

      //and disk[s] into smallDiff

      smallDiff = abs(disk[new_head] - disk[s]);

      //absolute difference disk[new_head]

      //and disk[l] into largeDiff

      largeDiff = abs(disk[l] - disk[new_head]);

      //check if smallDiff is lessthan largeDiff

      if (smallDiff < largeDiff)

      {//then add smallDiff to headMovement

          headMovement += smallDiff;

          new_head = s;

          s--;//Decrement s

      }

      else

      {//else add largeDiff to headMovement

          headMovement += largeDiff;

          new_head = l;

          l++;//increament l

      }

      n--;

  }

  //return head movments of SSTF

  return headMovement;

}

int discSchedAlgSCAN(int * ranArray) {

  int i = 0, currentValue = 0;

  int savedValue = disk[initialHead], difference = 0;

  int headMovement = 0, curr_i = 0;

  for (i = initialHead - 1; i >= 0; --i)

  {

      currentValue = disk[i];

      //absolute difference value saved and current values

      difference = abs(savedValue - currentValue);

      //add difference to the head movment

      headMovement += difference;

      //save the current value as saved value

      savedValue = currentValue;

  }

  /* used to subtract value from zero, or just add same value */

  headMovement += savedValue;

  savedValue = 0;

  for (i = initialHead + 1; i < REQUESTS; i++)

  {

      currentValue = disk[i];

      //absolute difference value saved and current values

      difference = abs(currentValue - savedValue);

      //add difference to the head movment

      headMovement += difference;

      //save the current value as saved value

      savedValue = currentValue;

  }

  //return head movments of SCAN

  return headMovement;

}

int discSchedAlgCSCAN(int *disk) {

  int i = 0, currentValue = 0;

  int savedValue = disk[initialHead], diff = 0;

  int headMovement = 0, lastIndex = 4999;

  for (i = initialHead + 1; i < REQUESTS; i++)

  {

      currentValue = disk[i];

      //absolute difference value saved and current values

      diff = abs(savedValue - currentValue);

      //add difference to the head movment

      headMovement += diff;

      //save the current value as saved value

      savedValue = currentValue;

  }

  //add last val - upper bound, go to and

  //add zero bounday (4999)

  headMovement += lastIndex - savedValue;

  savedValue = 0;

  headMovement += 4999;

  for (i = 0; i < initialHead; i++)

  {

      currentValue = disk[i];

      //absolute difference value saved and current values

      diff = abs(currentValue - savedValue);

      //add difference to the head movment

      headMovement += diff;

      savedValue = currentValue;

  }

  return headMovement;

}

int discSchedAlgLOOK(int* ranArray)

{

  int i = 0, currentValue = 0;

  int savedValue = disk[initialHead], diff = 0;

  int headMovement = 0, curr_i = 0;

  for (i = initialHead + 1; i < REQUESTS; i++)

  {

      currentValue = disk[i];

      //absolute difference value saved and current values

      diff = abs(savedValue - currentValue);

      headMovement += diff;

      savedValue = currentValue;

  }

  for (i = initialHead - 1; i >= 0; --i)

  {

      currentValue = disk[i];

      //absolute difference value saved and current values

      diff = abs(currentValue - savedValue);

      //add difference to the head movment

      headMovement += diff;

      savedValue = currentValue;

  }

  //return head movments of LOOK

  return headMovement;

}

int discSchedAlgCLOOK(int* ranArray)

{

  int i = 0, currentValue = 0;

  int savedValue = disk[initialHead];

  int diff = 0;

  int headMovement = 0;

  for (i = initialHead + 1; i < REQUESTS; i++)

  {

      currentValue = disk[i];

      //absolute difference value saved and current values

      diff = abs(savedValue - currentValue);

      //add difference to the head movment

      headMovement += diff;

      //save the current value as saved value

      savedValue = currentValue;

  }

  for (i = 0; i < initialHead; i++)

  {

      currentValue = disk[i];

      //absolute difference value saved and current values

      diff = abs(currentValue - savedValue);

      //add difference to the head movment