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                 DataPath 1.2

                  by

                 Bruce Dubbs
                 GDC Software
               122 Valencia Dr.
               Universal City, TX 78148







               DataPath Topics

        Purpose.....................................2

        System Requirements.........................2

        How to use DataPath.........................2

        Examples....................................3

        Features....................................5

        Technical Details...........................6

        Limitations.................................7

        References..................................7

        Disclaimer..................................8

        Modification History........................9

        Suggestions for use........................10


Page 2                        DataPath - GDC Software



                   Purpose

    DataPath is used to specify directories, other than the current
one, to be searched by executing programs, in the event that a file
that needs to be read cannot be found in the current directory.


             System Requirements

    DataPath requires 2162 bytes of disk space ( 5 512-byte sectors).
It becomes memory resident the first time it is run and increases the
size of the operating system by 1440 bytes.  It will run on any com-
puter using the MS-DOS or PC-DOS operating systems version 2.0 or
higher.


             How to use DataPath


    Entry Form

    DATAPATH [d:][pathname [;[d:]pathname]...][/x]

    where  'd' is the letter of the designated disk drive; and
        pathname' is a sequence of characters of the form:

        [\][directory][\directory...][\]

        Optionally you may use the MS-DOS shorthand notation
        shown below in lieu of 'directory':

        .    MS-DOS uses this shorthand symbol to indicate the name
        of the current working directory.  MS-DOS automati-
        cally creates this entry when a directory is made.

        ..    MS-DOS uses this shorthand symbol to indicate the name
        of the current directory's parent directory.  MS-DOS
        automatically creates this entry when a directory is
        made.

        Note: The two shorthand symbols do not exist in the root
        directory.

        /x is one or more of the following switches:

          /V, verbose mode, or
          /Q, quiet mode, or
          /R, allow file opens for read only, or
          /W, allow file opens for read or write, or
          /H, display help information.


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    Example 1

        If you are in directory \DATA and you want to use your
     copy of dBASE II which is in subdirectory \DBASE to work on
     data in your current directory, use the following sequence of
     commands:

        DATAPATH \DBASE<return>
        PATH \DBASE<return>
        DBASE<return>

    Example 2

        If you want to see the current DataPath, type:

        DATAPATH<return>

        The current DataPath will be displayed.

    Example 3

        If you want to disable DataPath type:

        DATAPATH   <return>

        One or more blanks should be typed after the command
     before the return.

    Example 4

        If you have all your DOS programs on a subdirectory named
     \DOS, Lotus 123 files in a subdirectory named \LOTUS, dBase
     files in a subdirectory named \DBASE, and an editor in a sub-
     directory named \EDITOR, and you want to access any of the
     programs from any subdirectory, use the following sequence:

        PATH     \DOS;\LOTUS;\DBASE;\EDITOR
        DATAPATH \DOS;\LOTUS;\DBASE;\EDITOR

        Note: This configuration will add a noticeable time delay
     to most applications that read files and to COMMAND.COM find-
     ing most programs. Using batch files to set PATH and DataPath
     is a much cleaner and quicker method.

Page 4                        DataPath - GDC Software

    Example 5

        If your programs are on disk A and your data is on disk B,
     use this sequence:

        PATH A:
        DATAPATH A:

        or alternatively to search both disks from either loca-
     tion:

        PATH A:;B:
        DATAPATH A:;B:

        This example assumes that all files on drives A and B are
     in the root directory.  Subdirectories are not of great use
     on 360K floppy disks, however, DataPath will work properly on
     floppy diskettes.

    Example 6

        You want to enable spelling dictionary files on subdirec-
     tory \WORD to be accessed when opened for writing and you
     want to suppress the DataPath messages:

        DATAPATH C:\WORD/W/Q

        Messages will remain suppressed until verbose mode is
     reset.

    Example 7

        You want to reset DataPath to search the \BIN subdirec-
     tory, disable opens for read, and reset verbose mode.

        DATAPATH C:\BIN/V/R

    Example 8

        You want to display quick help information about the data
     path and its switches.

        DATAPATH /h

        The data path will not be updated if the /h switch is pre-
     sent.


Page 5                        DataPath - GDC Software

                   Features

        DataPath supports the following features:

        1.    DataPath will ignore invalid drives or path specifica-
     tions.

        2.    DataPath has a very small size.  When installed, it
     uses only 1440 bytes of RAM.

        3.    DataPath will skip over a drive listed in the DataPath
     if the drive door is left open.  You will have to wait for
     the disk to time out, however.  You will get the normal
     Abort, Retry, Ignore command if the default drive door is
     open.

        4.    THE SOURCE TO DataPath IS RELEASED TO THE PUBLIC
     DOMAIN!

        5.    DataPath works on any MS-DOS or PC-DOS system. (Ver-
     sion 2.0 or higher.)  It is not dependent on hardware.

        6.    DataPath is compatible with CP/M style function calls
     in MS-DOS for older programs such as dBase II.

Page 6                        DataPath - GDC Software

                   Technical Details

        DataPath was written in assembly language and was optim-
     ized for both small size and fast operation.  The source for
     the program is in the file DP12.ASM.

        DataPath works by intercepting three different function
     calls to the operating system.  These are 'OPEN', 'FILE
     SIZE', and 'OPEN FILE HANDLE'.  The usual call within MS-DOS
     now is 'OPEN FILE HANDLE', but some programs use the older
     functions.  Lotus 1-2-3 Version 1A, for instance, uses 'FILE
     SIZE' to open a file.

        DataPath also intercepts older CP/M style call to the
     operating system, converts the calls to MS-DOS calls, and
     executes accordingly. The dBase II program uses this method.

        DataPath uses the 256 byte PSP (program segment prefix)
     that is left resident when the program installs itself.  It
     uses the space for storing the DataPath and for working
     space.



        The program logic for DataPath is as follows:

        1.    If DataPath is not interested in the function, pass it
     to DOS undisturbed.

        2.    Try the function.  If successful, return to the call-
     ing program.

        3.    If the file is to be opened for writing and the /R
     option (open for read only) is in effect, return.

        4.    If the path of the desired file is specified, return.
     If the program knows enough to specify a path, DataPath will
     not interfere. DataPath WILL search if only the disk drive is
     specified.

        5.    Search for the file along the DataPath.  If not found,
     return the error code found in step 2.  If found, complete
     the function and return to the calling program.

Page 7                        DataPath - GDC Software


                  Limitations

        Listed below are the known limitations of DataPath:

        1.    The maximum length of the DataPath string is 118 char-
     acters. This is due to the 127 character limitation MS-DOS
     puts on input strings.

        2.    DataPath cannot be uninstalled without rebooting the
     system. This should not be a problem because of its small
     size.    DataPath can be disabled by making the DataPath string
     blank.

        3. The DataPath will not accept wildcards.    They will be
     ignored.

        4.    DataPath will not create aliases for pathnames.

        5.    DataPath will not automatically search subdirectories
     beneath the specified directory.


                  References

        The following magazine article contains information on
     utilities that do the same function as DataPath:

        PC Tech Journal - April 1985 - pp 139-145.
        "File Search Help for PC-DOS" by Arthur A. Gleckler


        The following  magazine article contains general informa-
     tion on resident utilities:

        PC World - June 1986 - pp 270-284.
        "Battle for the Background" by Bruce Owen


        The following programs perform the same basic function as
     DataPath.  They contain different features, however their
     basic intent is the same as DataPath.

        DPath30   - Public Domain - No source

        FilePath  - Commercial  - $ 37.50
        Scout     - Commercial  - $ 29.95
        SuperPATH - Commercial  - $ 39.95
        EasyPath  - Commercial  - $100.00

Page 8                        DataPath - GDC Software


                  Disclaimer

        There is no copyright associated with this program.  It
     is, however, intended for private noncommercial distribution
     only.    You may make copies freely and use the source code in
     any manner that you wish. Please do not charge anyone for
     this program.    It is free.

        This software is not warranted in any manner.  No guaran-
     tee is made that the program operates as it was designed.  I
     will not be liable for any damages that may occur by using
     this program.    If you use the program, you agree to this.

        Any comments, suggestions, or criticisms are welcome.
     Examples of conflicts with other memory resident utilities or
     the inability of DataPath to work with a particular program
     are especially welcome.  I can be normally be reached at the
     following:
        Telstar Bulletin Board [phone]
        SAHUG Bulletin Board   [phone]
        Compuserve ID: 72330,123

        If you distribute this program, or a modification of this
     program, it would be nice for you to acknowledge the source.

                  Bruce Dubbs
                 GDC Software
                   122 Valencia Dr.
               Universal City, TX 78148
                   September 2, 1986


Page 9                        DataPath - GDC Software


                 Modification History

        Version 1.0 - September 2, 1986 - Original release.

        Version 1.1 - September 18, 1986 - Add /Q, /V, /W, and /R
              switches.  Allow DataPath to be searched if
              disk drive is specified in ASCIIZ file spe-
              cification.

        Version 1.2 - October 9, 1986 - Add /H switch.  Improve
              memory resident check for compatability with
              other GDC memory resident utilities.


Page 10                     DataPath - GDC Software



              Suggestions for use

        The best way to use DataPath is to organize your disk
     subdirectories such that the executable and supporting files
     are on a different subdirectory than the data files.  The
     best example is WordStar.  If you put the WordStar executable
     and overlays in a subdirectory 'WORDSTAR' and have your data
     files in other subdirectories, the following benefits occur:

     1.  You can execute WordStar from ANY subdirectory.
     2.  You do not have to look for your data files intermixed
         with executable and overlay files.

        To do this, set the following to execute in the
     AUTOEXEC.BAT file that executes when you boot MS-DOS.

        PATH \WORDATAR
        DATAPATH \WORDSTAR
        WS

        This procedure can be generalized to any set of programs
     and overlays.    To keep from setting multiple paths for all
     searches, a set of batch files can be created such as the
     following file that executes dBase III.


     DO.BAT:    echo off
            datapath c:\dbase
            path c:\dbase
            dbase %1
            path c:\bin;c:\batch
            datapath c:\bin

        This example assumes the dBase executable files are in the
     directory \dbase, the batch file DO.BAT is in the directory
     \batch, the MS-DOS executable files are in \bin and the data
     for dBase are in the current directory.

     For more information on batch files, consult the MS-DOS
     manual.