C++ Program on Merge Sort

      #include <iostream.h>
   int a[50];
   void merge(int,int,int);
   void merge_sort(int low,int high)
   {
     int mid;
     if(low<high)
     {
       mid=(low+high)/2;
       merge_sort(low,mid);
       merge_sort(mid+1,high);
       merge(low,mid,high);
     }
   }
   void merge(int low,int mid,int high)
   {
     int h,i,j,b[50],k;
     h=low;
     i=low;
     j=mid+1;
     while((h<=mid)&&(j<=high))
     {
       if(a[h]<=a[j])
       {
         b[i]=a[h];
         h++;
       }
       else
       {
         b[i]=a[j];
         j++;
       }
       i++;
     }
     if(h>mid)
     {
       for(k=j;k<=high;k++)
       {
         b[i]=a[k];
         i++;
       }
     }
     else
     {
       for(k=h;k<=mid;k++)
       {
         b[i]=a[k];
         i++;
       }
     }
     for(k=low;k<=high;k++)
     a[k]=b[k];
   }
   void main()
   {
     int num,i;
     cout<<"MERGE SORT PROGRAM"<<endl;
     cout<<"Please Enter THE NUMBER OF ELEMENTS you want to sort [THEN
     PRESS ENTER]:"<<endl;
     cin>>num;
     cout<<endl;
     cout<<"Now, Please Enter the ( "<< num <<" ) numbers (ELEMENTS) [THEN
     PRESS ENTER]:"<<endl;
     for(i=1;i<=num;i++)
     {
       cin>>a[i] ;
     }
     merge_sort(1,num);
     cout<<endl;
     cout<<"So, the sorted list (using MERGE SORT) will be :"<<endl;
     cout<<endl<<endl;
     for(i=1;i<<=num;i++)
     cout<<a[i]<<" ";
     cout<<endl<<endl<<endl<<endl;
   }