Q.1 Write a program to simulate Sequential (Contiguous) file allocation method.
Assume disk with n number of blocks. Give value of n as input. Randomly mark some
block as allocated and accordingly maintain the list of free blocks Write menu driver
program with menu options as mentioned below and implement each option.
• Show Bit Vector
• Show Directory
• Delete File
• ExIT

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAX 200
typedef struct dir
{
char fname[20];
int start;
struct dir *next;
}NODE;
NODE *first,*last;
int n,fb,bit[MAX];
void init()
{ int
i;
printf("Enter total no.of disk blocks:");
scanf("%d",&n);
fb = n;
for(i=0;i<10;i++)
{
int k = rand()%n;
if(bit[k]!=-2)
{
bit[k]=-2;
// fb--;
}
}
}
void show_bitvector()
{
int i;
for(i=0;i<n;i++)
printf("%d ",bit[i]);
printf("\n");
}
void show_dir()
{
NODE *p;
int i;
printf("File\tChain\n");

p = first;
while(p!=NULL)
{
printf("%s\t",p->fname);
i = p->start; while(i!=-1)
{
printf("%d->",i);
i=bit[i];
}
printf("NULL\n");

p=p->next;
}
}
void create()
{
NODE p; char
fname[20]; int
i,j,nob;
printf("Enter file name:");
scanf("%s",fname);
printf("Enter no.of blocks:");
scanf("%d",&nob);
if(nob>fb)
{
printf("Failed to create file %s\n",fname);
return;
}
for(i=0;i<n;i++)
{
if(bit[i]==0) break;
}
p = (NODE)malloc(sizeof(NODE));
strcpy(p->fname,fname);
p->start=i;
p->next=NULL;
if(first==NULL)
first=p; else
last->next=p;
last=p;
fb-=nob;
j=i+1; nob--
;
while(nob>0)
{
if(bit[j]==0)
{
bit[i]=j;
i=j;
nob--;
}
j++;
}
bit[i]=-1;
printf("File %s created successully.\n",fname);
}
void delete()
{
char fname[20];
NODE *p,*q; int
nob=0,i,j;
printf("Enter file name to be deleted:");
scanf("%s",fname);
p = q = first;
while(p!=NULL)
{
if(strcmp(p->fname,fname)==0)
break;
q=p; p=p-

next;
}
if(p==NULL)
{
printf("File %s not found.\n",fname);
return;
}
i = p-
start;
while(i!=-1)
{
nob++;
j = i; i =
bit[i]; bit[j] = 0;
}
fb+=nob;

if(p==first) first=first-

next;
else if(p==last)
{
last=q;
last->next=NULL;
}
else q->next = p-
next;
free(p);

printf("File %s deleted successfully.\n",fname);
}
int main()
{ int
ch;
init();
while(1)
{
printf("1.Show bit vector\n");
printf("2.Create new file\n");
printf("3.Show directory\n");
printf("4.Delete file\n");
printf("5.Exit\n"); printf("Enter
your choice (1-5):");
scanf("%d",&ch);
switch(ch)
{
case 1:
show_bitvector();
break;
case 2:
create();
break; case
3:
show_dir();
break; case
4: delete();
break; case
5: exit(0);
}
}
return 0;
}

Q2Q.2 Write a simulation program for disk scheduling using SSTF algorithm. Accept total
number of disk blocks, disk request string, and current head position from the user. Display
the list of request in the order in which it is served. Also display the total number of head
moments.
55, 58, 39, 18, 90, 160, 150, 38, 184
Start Head Position: 50
ANS

include<stdio.h>

#include<stdlib.h>
int main()
{
int RQ[100],i,n,TotalHeadMoment=0,initial,count=0;
printf("Enter the number of Requests\n");
scanf("%d",&n);
printf("Enter the Requests sequence\n");
for(i=0;i<n;i++)
scanf("%d",&RQ[i]);
printf("Enter initial head position\n");
scanf("%d",&initial);
printf("%d-",initial);
while(count!=n)
{
int min=1000,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];
printf("------->%d",RQ[index]);
// 1000 is for max
// you can use any number
RQ[index]=1000;
count++;
}
printf("\nTotal head movement is %d",TotalHeadMoment);
return 0;
}