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
