Объединить два файла

 Procedure ConCatFiles(Const targetname: String;
                       Const Sourcenames: Array of String);
   Var
     i: Integer;
     target, source: TFileStream;
   Begin
     target := TFileStream.Create( targetname, fmCreate );
     try
       For i:= Low(Sourcenames) To High(Sourcenames) Do Begin
         source := TFileStream.Create( Sourcenames[i],
                                       fmOpenread or fmShareDenyNone );
         try
           target.Copyfrom( source, 0 );
         finally
           source.free;
         end
       End;
     finally
       target.Free;
     end;
   End;

  chDir(ExtractFileDir(Application.Exename));
  ConcatFiles('sum.txt', ['project1.dpr','unit1.pas','unit2.pas']);