Function Ptr2Long(p: Pointer): LongInt; Assembler;
Asm
   mov ax,word ptr [p+2]
   mov dx,ax
   shr dx,12
   shl ax,4
   add ax,word ptr [p]
   adc ax,0
End;

Function Long2Ptr(l: LongInt): Pointer; Assembler;
Asm
   mov ax,word ptr [l]
   mov dx,word ptr [l+2]
   mov bx,ax
   and ax,0Fh
   shr bx,4
   shl dx,12
   add dx,bx
End;

Function SubPtr(p: Pointer; d: LongInt): Pointer;
Begin
  SubPtr := Long2Ptr(Ptr2Long(p)-d);
End;

Function AddPtr(p: Pointer; d: LongInt): Pointer;
Begin
  AddPtr := Long2Ptr(Ptr2Long(p)+d);
End;