Program in c++ to perform First Fit , Best Fit and Worst Fit

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.

Program (Source Code) :

<pre class="brush: html">

#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 :