Before learning programming concept of First , best & Worst Fit we should know about these Operating System Concept.
First fit: The allocator places a process in the First block of unallocated memory in which it will fit.
Best fit: The allocator places a process in the smallest block of unallocated memory in which it will fit.
Worst fit: The memory manager places a process in the largest block of unallocated memory available.
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First fit: The allocator places a process in the First block of unallocated memory in which it will fit.
Best fit: The allocator places a process in the smallest block of unallocated memory in which it will fit.
Worst fit: The memory manager places a process in the largest block of unallocated memory available.
Program (Source Code) :
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#include<conio.h>
#include<iostream.h>
int main()
{
int c,i,j,k,n,l,m[10],p[10],po[20],flag,z,y,temp,temp1;
cout<<"enter memory partition:\t";
cin>>n;
cout<<"\nenter memory size for\n";
for(i=1;i<=n;i++)
{
cout<<"\npartition "<<i<<" :\t";
cin>>m[i];
po[i]=i;
}
cout<<"\nenter process:\t";
cin>>j;
cout<<"\nenter memory size for\n";
for(i=1;i<=j;i++)
{
cout<<"\nprocess "<<i<<" :\t";
cin>>p[i];
}
cout<<"\n******** welcome to menu driven program of memory management**********\n1.first fit\n2.best fit\n3.worst fit\nenter choice:\t";
cin>>c;
switch(c)
{
case 1:
for(i=1;i<=j;i++)
{
flag=1;
for(k=1;k<=n;k++)
{
if(p[i]<=m[k])
{
cout<<"\nprocess "<<i<<" whose memory size is "<<p[i]<<"KB allocated at memory partition:\t"<<po[k];
m[k]=m[k]-p[i];
break;
}
else
{
flag++;
}
}
if(flag>n)
{
cout<<"\nprocess "<<i<<" whose memory size is "<<p[i]<<"KB can't be allocated";
}
}
break;
case 2:
for(y=1;y<=n;y++)
{
for(z=y;z<=n;z++)
{
if(m[y]>m[z])
{
temp=m[y];
m[y]=m[z];
m[z]=temp;
temp1=po[y];
po[y]=po[z];
po[z]=temp1;
}
}
}
for(i=1;i<=j;i++)
{
flag=1;
for(k=1;k<=n;k++)
{
if(p[i]<=m[k])
{
cout<<"\nprocess "<<i<<" whose memory size is "<<p[i]<<"KB allocated at memory partition:\t"<<po[k];
m[k]=m[k]-p[i];
break;
}
else
{
flag++;
}
}
if(flag>n)
{
cout<<"\nprocess "<<i<<" whose memory size is "<<p[i]<<"KB can't be allocated";
}
}
break;
case 3:
for(y=1;y<=n;y++)
{
for(z=y;z<=n;z++)
{
if(m[y]<m[z])
{
temp=m[y];
m[y]=m[z];
m[z]=temp;
temp1=po[y];
po[y]=po[z];
po[z]=temp1;
}
}
}
for(i=1;i<=j;i++)
{
flag=1;
for(k=1;k<=n;k++)
{
if(p[i]<=m[k])
{
cout<<"\nprocess "<<i<<" whose memory size is "<<p[i]<<"KB allocated at memory partition:\t"<<po[k];
m[k]=m[k]-p[i];
break;
}
else
{
flag++;
}
}
if(flag>n)
{
cout<<"\nprocess "<<i<<" whose memory size is "<<p[i]<<"KB can't be allocated";
}
}
break;
}
getch();
return 0;
}</pre>
Output Screen :
