This is a program for the implementation of Best fit, Worst Fit, and First Fit for the operating systems lab. If you have any doubts please let me know.
#include<stdio.h>
#include<stdlib.h>
int
i,j,n,x,ch,size,ch1,ch2,y,pid;
struct alloc1
{
int id,sa,ea,size;
struct alloc1 *next;
}*start=NULL,*ptr=NULL,*newn=NULL;
struct free1
{
int stadd,eadd,size1;
struct free1 *next;
}*start1=NULL,*newn1=NULL,*ptr2=NULL,*preptr2=NULL;
void
displayfree(struct free1 *temp)
{
printf("\n\nFree
Space\n");
temp=start1;
while(temp!=NULL)
{
printf("%d",temp->stadd);
printf(" - %d\n",temp->eadd);
temp=temp->next;
}}
void
display(struct alloc1 *temp1)
{
printf("\n\nAllocated\n");
temp1=start;
while(temp1!=NULL)
{
printf("p%d\t",temp1->id);
printf("%d",temp1->sa);
printf(" - %d\n",temp1->ea);
temp1=temp1->next;
}
}
void init()
{
newn->sa=ptr2->stadd;
newn->ea=newn->sa+size-1;
ptr2->stadd=ptr2->stadd+size;
ptr2->size1=ptr2->size1-size;
}
void main()
{
printf("\nEnter the number of
processes:\n");
scanf("%d",&n);
for(i=0;i<n;i++)
{
newn=(struct alloc1 *)
malloc(sizeof(struct alloc1));
printf("\nEnter process id:
");
scanf("%d",&newn->id);
printf("\nEnter the start
address: ");
scanf("%d",&newn->sa);
printf("\nEnter the end address:
");
scanf("%d",&newn->ea);
newn->size=(newn->ea-newn->sa)+1;
if(start==NULL)
{
start=newn;
start->next=NULL;
ptr=start;
}
else
{
while(ptr->next!=NULL)
{
ptr=ptr->next;
}
ptr->next=newn;
ptr=ptr->next;
ptr->next=NULL;
}
}
printf("\nEnter the details of free
space\n");
do
{
newn1=(struct free1 *) malloc(sizeof(struct
free1));
printf("\nEnter the starting address:
");
scanf("%d",&newn1->stadd);
printf("\nEnter the ending address:
");
scanf("%d",&newn1->eadd);
newn1->size1=(newn1->eadd-newn1->stadd)+1;
if(start1==NULL)
{
start1=newn1;
start1->next=NULL;
ptr2=start1;
}
else
{
while(ptr2->next!=NULL)
ptr2=ptr2->next;
ptr2->next=newn1;
ptr2=ptr2->next;
ptr2->next=NULL;
}
ptr2=start1;
printf("\nPress 1 to add more...");
scanf("%d",&ch);
}while(ch==1);
printf("\n
BEFORE FITTING\n");
displayfree(ptr2);
ptr=start;
display(ptr);
do
{
printf("\nEnter the size of new process:
");
scanf("%d",&size);
printf("\nEnter the process id:");
scanf("%d",&pid);
newn=((struct alloc1 *)malloc(sizeof(struct
alloc1)));
newn->next=NULL;
newn->size=size;
newn->id=pid;
printf("\nMENU:\n1.First fit\n2.Best
fit\n3.Worst fit\n4.Exit\n");
printf("\nEnter your
choice:\n");
scanf("%d",&ch1);
switch(ch1)
{
case 1:
ptr2=start1;
if(ptr2->size1==size)
{
start1=ptr2->next;
}
else
{
while(ptr2->size1<size)
{
if(ptr2->next==NULL)
{
printf("\nInsufficient
memory");
goto lab;
}
preptr2=ptr2;
ptr2=ptr2->next;
if(ptr->size==size)
{
preptr2->next=ptr2->next;
}}}
init(); ptr=start;
while(ptr->next!=NULL)
ptr=ptr->next;
ptr->next=newn;
printf("\nFIRST FIT\n");
display(ptr);
displayfree(ptr2);
lab: break;
case 2:
ptr2=start1;
x=1000;
while(ptr2!=NULL)
{
if((ptr2->size1>=size)&&(ptr2->size1<=x))
{
x=ptr2->size1;
}
ptr2=ptr2->next;
}
if(x==1000)
{
printf("\nInsufficient memory");
break;
}
ptr2=start1;
while(ptr2->size1!=x)
{
preptr2=ptr2;
ptr2=ptr2->next;
}
init();
if(x==size)
preptr2->next=ptr2->next;
ptr=start;
while(ptr->next!=NULL)
ptr=ptr->next;
ptr->next=newn;
printf("\nBEST FIT\n");
display(ptr);
displayfree(ptr2);
break;
case 3:
ptr2=start1;
y=0;
while(ptr2!=NULL)
{
if((ptr2->size1>=size)&&(ptr2->size1>=y))
{
y=ptr2->size1;
}
ptr2=ptr2->next;
}
if(y==0)
{
printf("\nInsufficient memory");
break;
}
ptr2=start1;
while(ptr2->size1!=y)
{
preptr2=ptr2;
ptr2=ptr2->next;
}
if(y==size)
{
preptr2->next=ptr2->next;
}
init(); ptr=start;
while(ptr->next!=NULL)
{
ptr=ptr->next;
}
ptr->next=newn;
printf("\nWORST FIT\n");
display(ptr);
displayfree(ptr2);
break;
case 4:break;
default:break;
}
printf("\npress
1 to add more..");
scanf("%d",&ch2);
}while(ch2==1);
}
