Assignment No:3

 Assignment No:3

Slot-I

 i. Write an OS program to implement FCFS Disk Scheduling algorithm. 

CODE:

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1. #include<stdio.h>
2. #include<stdlib.h>
3. void main()
4. {
5. int req[20],cpos,i,n,j,index,dir,temp,headmove=0,size=200;
6. printf("\nEnter number of requests");
7. scanf("%d",&n);
8. printf("\n Enter request ");
9. for(i=0;i<n;i++)
10. scanf("%d",&req[i]);
11. printf("\nEnter curreent position");
12. scanf("%d",&cpos);
13. for(i=0;i<n;i++)
14.   {
15.    headmove=headmove+abs(cpos-req[i]);
16.    cpos=req[i];
17.    }
18.    printf("\nNumber of head movements=%d",headmove);
19. }

ii. Write an OS program to implement SSTF algorithm Disk Scheduling algorithm. 

CODE:

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1. #include<stdio.h>
2. #include<stdlib.h>
3. 
   
4. int main()
5. {
6.  int req[20],cpos,i,n,headmove=0,index,count=0,min,d;
7.  printf("Enter the number of requests\n");
8.  scanf("%d",&n);
9.  printf("Enter the sequence of requests\n");
10.  for(i=0;i<n;i++)
11.  scanf("%d",&req[i]);
12.  printf("Enter initial head position\n");
13.  scanf("%d",&cpos);
14.  while(count!=n)
15.  {
16.  int min=1000,d,intex;
17.  for(i=0;i<n;i++)
18.    {
19.      d=abs(req[i]-cpos);
20.      if(min>d)
21.       {
22. min=d;
23. index=i;
24.    }
25.   }
26.   headmove=headmove+min;
27.   cpos=req[index];
28.     req[index]=1000;
29.     count++;
30.  }
31.  
32.  printf("Total head movements is %d",headmove);
33.  return 0;
34. }

Slot-II 

i. Write an OS program to implement SCAN Disk Scheduling algorithm. 

CODE:

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1. #include<stdio.h>
2. #include<stdlib.h>
3. 
   
4. int main()
5. {
6.  int req[20],cpos,i,n,headmove=0,index,dir,j,temp,size=20;
7.  printf("Enter the number of requests\n");
8.  scanf("%d",&n);
9.  printf("Enter the sequence of requests\n");
10.  for(i=0;i<n;i++)
11.  scanf("%d",&req[i]);
12.  printf("Enter initial head position\n");
13.  scanf("%d",&cpos);
14.  printf("Enter head movement direction 0 for left and 1 for right");
15.  scanf("%d",&dir);
16.  req[n]=cpos; 
17.  n=n+1;  
18.  
19.  //sort request array
20.  
21.  for(i=0; i<n; i++)
22.  {
23.    for(j=i+1; j<n; j++)
24.     { 
25.       if(req[i]>req[j])
26.       {
27.         temp=req[i];
28.         req[i]=req[j];
29.         req[j]=temp;
30.        }
31.     }
32.  }
33.  for(i=0; i<n; i++)
34.  {
35.   if(req[i]==cpos)
36.   {
37.     index=i;
38.     break;
39.   }
40.  }
41. if(dir==0)
42. {
43.  for(i=index-1; i>=0; i--)
44.  {
45.    headmove=headmove+abs(cpos-req[i]);
46.    cpos=req[i];
47.   }
48.  headmove=headmove+(cpos-0);
49.  cpos=0;
50.  for(i=index+1; i<n; i++)
51.  {
52.    headmove=headmove+abs(cpos-req[i]);
53.    cpos=req[i];
54.   }
55. }
56. 
    
57. else if(dir==1)
58. {
59.   for(i=index+1; i<n; i++)
60.    {
61.     headmove=headmove+abs(cpos-req[i]);
62.     cpos=req[i];
63.   }
64.  headmove=headmove+(cpos-(size-1));
65.  cpos=(size-1);
66.  for(i=index-1; i>=0; i--)
67.  {
68.    headmove=headmove+abs(cpos-req[i]);
69.    cpos=req[i];
70.    }
71.   }
72. printf("\nNumber of head movements=%d",headmove);
73. }

ii. Write an OS program to implement C-SCAN algorithm Disk Scheduling algorithm.

CODE:

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