TYBcs OS-Syspro Slip 18-2 | IProgramX

#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;
}