EXE2COM.txt

                                  EXE2COM 1.04
                         By Chris Dunford/Cove Software

        | indicates information changed/added in recent versions.

        Purpose
        -------
        EXE2COM is a one-for-one replacement for the EXE2BIN program
        that was formerly distributed with DOS.  Beginning with DOS 3.3,
        EXE2BIN has been moved to the disk that comes with the DOS
        Technical Reference and thus is not available without extra
        cost.


        Usage
        -----
        Usage is identical to DOS's EXE2BIN except that the output file
        extension defaults to COM rather than BIN, and there is an
        optional switch that displays EXE file information rather than
        converting the file to COM.

        Complete usage is:

            EXE2COM [/I] [d:][path]file[ext] [d:][path][file][ext]

        The drive and path of the first file default to the current
        drive and path, if not specified.  The extension of the first
        file defaults to EXE, if not specified.

        If the second file is completely unspecified, it defaults to the
        same drive, path, and filename as the first, except that the
        extension will be COM.

        If the second file is specified but without an extension, COM
        will be assumed (this is different from EXE2BIN).

      | If /I is specified, information about the EXE file is displayed
      | and no conversion is performed.  The output file name, if
      | specified, is ignored.

        The simplest (and usual) usage is simply:

            EXE2COM file

        which will take the named EXE file in the current directory and
        convert it to a COM file in the same directory.


        Operation
        ---------
        EXE2COM runs the same way as EXE2BIN, with the following
        exceptions:

            1. The binary fixup option of EXE2BIN (IP=0, segment fixups
            required) is not supported.

            2. The EXE file checksum is not verified.

            3. Error messages are more useful, and a warning is provided
            if a COM file is created with an initial IP other than 100H.

            4. The default output file extension is COM rather than BIN.


      | Information display
      | -------------------
      | If you use the /I switch, EXE2COM just displays information
      | about the EXE file and does not attempt to convert it to COM
      | (therefore, the EXE file need not be a convertible file).  Here
      | is a typical display, resulting from running EXE2COM on itself
      | (version 1.04) with the /I switch:
      |
      |   exe2com.exe                   (hex)      (dec)
      |     EXE file size                396B      14699
      |     EXE header size (para)         20         32
      |     Program image size (bytes)   376B      14187
      |     Minimum load size (bytes)    8CDB      36059
      |     Min allocation (para)         557       1367
      |     Max allocation (para)        FFFF      65535
      |   * Initial CS:IP           0000:072C
      |   * Initial SS:SP           084D:0800       2048 (stack size)
      |   * Relocation count                4          4
      |     Relo table start             001E         30
      |     EXE file checksum            411D      16669
      |     Overlay number                  0          0
      |   * = this item prevents conversion to BIN/COM
      |
      | The fields that may need some explanation:
      |
      | Program image size:  this is the size of the program itself
      | (i.e., the size of the EXE file less the size of the header
      | information).  This much memory is required to load a copy of
      | the program's code and pre-allocated data.
      |
      | Minimum load size: at least this much free memory is required in
      | order to run the program.
      |
      | Min/max allocation: the minimum/maximum number of 16-byte
      | paragraphs that will be needed above the end of the program
      | image when it is loaded.  Minimum load size is the sum of the
      | program image size and the minimum allocation.
      |
      | If an item is starred (*), this prevents the EXE file from being
      | converted to a COM file.


        Error Messages
        --------------
        These are EXE2COM's error messages.  If one of these is seen,
        the EXE file will not be converted and the errorlevel returned
        by EXE2COM will be 1.

        ERROR READING EXE HEADER
            EXE2COM was unable to read the EXE file header from disk.

        ERROR WRITING OUTPUT FILE
            EXE2COM was unable to write the converted file to disk.

        INVALID EXE FILE SIGNATURE
            The first two bytes of an EXE file should be ASCII 'M' and
            'Z'.  This was not the case, and it's probably not an EXE
            file.

        EXE HAS RELOCATABLE ITEMS
            In order to be converted to a COM file, an EXE file cannot
            have any direct references to segments.  For example, the
            assembler instruction "mov ax,code" (where CODE is a segment
            name) is a segment reference.  One or more segment
            references were found in the EXE file.

        EXE HAS STACK SEGMENT
            In order to be converted to a COM file, an EXE file cannot
            have a stack segment.

        EXE HAS NONZERO CS
            In order to be converted to a COM file, an EXE file must
            have a code segment that begins at offset 0 of the code
            image in the EXE file.

        IP NOT 0 OR 100H
            In order to be converted to a binary file, an EXE file must
            have an entry point of 0 or 100H within the code segment.
            For COM files, the entry point should be 100H.  For SYS
            files (device drivers), the entry point should be 0.

        PROGRAM EXCEEDS 64K
            In order to be converted to a binary file, the total size of
            the code to be loaded (including the PSP) must not exceed
            64K bytes.

        UNKNOWN ERROR
            Internal error.  Notify the author.


        Warning message
        ---------------
        EXE2COM has one warning message:

            COM FILE, INITIAL IP NOT 100H

        The entry point of all COM files should be 100H.  If you are
        creating a COM file an the entry point is not 100H, EXE2COM will
        do the job but let you know that there is a potential problem.


        Source
        ------
        Source code should be included with this archive.  Users are
        encouraged to modify, improve, and/or correct the source for
        EXE2COM and submit the new program to the author for
        distribution.  Please identify clearly any changes made and
        stick with portable code (no inline assembler, PLEASE).

        Source for EXE2COM was written for the Microsoft C compiler
        (v.5.0) but will also compile correctly with Borland's Turbo C
        (v.1.5).  It should be easily portable to most other compilers.


        Public domain
        -------------
        EXE2COM is hereby donated by the author to the public domain.


        History
        -------
        Version 1.00 04/17/87: Original version by
            Christopher J. Dunford
            The Cove Software Group
            PO Box 1072
            Columbia, MD 21044
            (301) 992-9371
            CompuServe 76703,2002

        Version 1.01: port to Turbo C by
            Roger Schlafly
            Borland International
            Scotts Valley, CA 95066
            CompuServe 76067,511

        Version 1.02 11/22/87: bug fix for even 512-byte file made to
        Turbo C port by
            Chris Blum ( Consultant )
            509 West Main, Front
            Ashland, Ohio 44805
            CompuServe 76625,1041

            Chris Dunford duplicated the fix in the C86 source.

        Version 1.03 12/30/87: by Chris Dunford
            Ported to Microsoft C 5.0.  This is now the "official"
            version.

            Increased size of I/O buffer to 4K for speed reasons.
            EXE2COM 1.03 is twice as fast as 1.02 and slightly
            faster than EXE2BIN.

        Version 1.04 03/08/88: by Chris Dunford
            Cleaned up some old code from the original quickie.

            Source should now compile under either MSC or TC.

            Added /I switch.

            In earlier versions, we defined an error code for nonzero
            CS, but didn't actually check; now we do.