------------------------------

                     INSIDE TURBO PASCAL UNIT FILES

                         Version 6.0 for MS-DOS
                        Version 1.0 for WINDOWS

                     ------------------------------

                                   by

                            William L. Peavy

                            ----------------

                              June 6, 1991



                                ABSTRACT

      If you  want to  know what is in a .TPU (unit) file produced
      by either  Version 1.0  of Turbo  Pascal for  Windows or  by
      Version 6.0 of Turbo Pascal from Borland International, then
      this paper  is for you.  It doesn't explain quite everything
      since the  I  don't  have  access  to  secret  documents  or
      anything like  that and since some of the data in .TPU files
      just doesn't  have enough  auxiliary information to make its
      role clear.   However,  it is possible to learn a great deal
      about how Turbo Pascal organizes the information it needs to
      refer to, and it is also possible to learn just what kind of
      code the compiler produces.

      This is  the fourth in a series of reports on the subject of
      Turbo Pascal Units, the previous reports treating with Turbo
      Pascal Versions  5.0 through  6.0.   The evolution  of these
      files  in   the  face  of  changing  requirements  has  been
      fascinating to  behold and  deciphering their  contents  has
      been challenging to say the least.

      The programs supplied with this report have been reorganized
      from their 6.0 style and many identifiers have been changed.
      There are also a few bug fixes and algorithm changes.  Other
      changes were  dictated by  the changes in the utilization of
      the TPU file itself by the Windows Compiler.

      Since I  have a "real" job which requires my full attention,
      and since  it doesn't  involve use  of these products in any
      direct way,  I am  usually hard-pressed to find the personal
      time to  conduct this  research.    Consequently,  I  always
      refuse to  commit to follow-up or even error correction.  It
      would  be  irresponsible  of  me  to  pretend  it  could  be
      otherwise.  Even so, this is a revised report which contains
      a few  error fixes  and discusses the newly enhanced program
      which incorporates  these fixes  and  sports  some  enhanced
      capabilities.


      What's NEW

06/03/91 - Code drastically re-structured.  Program now supports
      units compiled by TURBO PASCAL for WINDOWS as well as TURBO
      Pascal Version 6.0.  Pointer manipulation code removed for
      safety.
      Listing format is (hopefully) improved and size is reduced.

      Program now retrieves units mentioned in "USES" statements and
      is thus able to provide actual type names (and Array bounds)
      when displaying most LG's.  Unit version numbers are checked.
      Source of each unit file successfully retrieved is also printed
      at beginning of run with the appropriate TURBO Library (.TPL)
      being searched if necessary to resolve referenced Units.

      Unit files of up to about 320 KB are now fully supported!

      Program now asks if the Unit is for WINDOWS or DOS and bases its
      .TPL Library search on the response.

      The index has been re-worked to include context info and to
      improve its utility.

      Several minor mistakes are also fixed in both the program and
      in its reports including a few minor disassembler bugs involving
      the AAM and AAD instructions.

      The technical report now describes many of the new features that
      are found in Units compiled by the WINDOWS compiler.



                Files on the Distribution Disk

Filename.x      Description of Contents
-----------     -------------------------------------------------
README.!!!      This file (you're reading it now)
WHATS.NEW       Description of new features and fixes, etc.

TWU1DOC.TXT     Report on Research (58 pages; copy to PRN:)

TWU1.EXE        The Supplied Program ready to run

TWU1.PAS        Turbo Pascal Source - The Main Program
TWU1EQU.PAS	Turbo Pascal Source - General-Purpose Stuff
TWU1RPT.PAS     Turbo Pascal Source - Text File Output Unit
TWU1UAM.PAS     Turbo Pascal Source - Access Methods for .TPU Files
TWU1UNA.PAS     Turbo Pascal Source - Disassembler Unit


                                The Author

This work was done by William L. Peavy, Houston Texas as a private
research endeavor.

I am interested in feedback, suggestions, constructive criticism,
and success stories.  I can be reached via Compuserve (70042,2310),
via the HAL-PC Telecom-1 BBS or via the HAL-PC Telecom-2 BBS.
Especially welcome is feedback regarding new discoveries that you
might make about .TPU files. 


Enjoy!