Example:
========

The state of compiler directives was not found to have any effect but is
included for reference.
{$A+,B-,C-,D-,E-,F-,G+,H+,I-,J+,K-,L-,M-,N+,O+,P+,Q-,R-,S-,T-,U-,V+,W+,X+,Y-
,Z1}
{$MINSTACKSIZE $00004000}
{$MAXSTACKSIZE $00100000}
{$IMAGEBASE $00400000}
{$APPTYPE CONSOLE}

Programme with bug, two files, a DPR-file and a unit PAS-file:
=====================BugPr.dpr==================
program BugPr;

uses
  BugUnit in 'BugUnit.pas';

procedure Go;
  Begin
  Writeln(MaxDim);
  end;

begin
  Go;
end.
=====================BugPr.dpr==================
=====================BugUnit.pas================
unit BugUnit;

interface

Const MaxDim = High(Cardinal);

implementation

end.
=====================BugUnit.pas================

Programme without bug, exactly the same, except the Const decleration is
moved to the DPR-file (so no unit PAS-file):
=====================NoBugPr.dpr================
program NoBugPr;

Const MaxDim = High(Cardinal);

procedure Go;
  Begin
  Writeln(MaxDim);
  end;

begin
  Go;
end.
=====================NoBugPr.dpr================

