UPCOMP COMMAND

Purpose: Compares and updates files basing on previous version.

Syntax:  UPCOMP <command>[/<sw>] <diff_list> [<old_names>] [<new_names>]

Type:    External command

Description:
     The procedure of comparison is the following: the program looks for
fragments coinciding in both versions and creates the comparison protocol.
This protocol contains records about the common fragments and about unique
byte sequences, that are absent in the old version. Based on this protocol,
the program then takes the unique new fragments from the comparison protocol
and adds them to already existing in old version coinciding fragments. If
the difference between versions is not very great, the size of protocol is
considerably less than the size of files compared, so updating files with
Upcomp program takes less time than copying new version.  Using this program
you can minimize costs of commercial networks and modem lines.

     As Upcomp program does not use data compressing, you may use any
additional archiver and save more disk space. (But do not try to compare
archived files with Upcomp, because archive copies of even very similar
files may have no common fragments at all.) Small size of program makes it
possible to include it also into archived package, and you may easily
automate updating procedure using selfunpacking archives with consequent
.BAT file starting.

     Starting this command without parameters displays brief information
about the command.

Parameters:

<command>    - the mode of Upcomp, which may be one of the following:

    c (compare)  - Compare files and create comparison protocol,
                   which name is specified in <diff_list> parameter;
    u (update)   - Update version, using old one and the comparison
                   protocol;
    l (list)     - Display the contents of comparison protocol;

/<sw>       - keys defining the method of comparison.  This parameter may
              be located in any place of the command line. Default key is
              /m2. Key /m0 corresponds to the best quality of comparison
              but at the lowest rate. In this case the comparison may take
              about one minute per every 100 Kb. Key /m4 reduces the time
              of comparison but perhaps also reduces the number of
              coincidences found.

<diff_list> - is the Path and filename of comparison protocol.

<new_names> and <old_names>
            - the pathes and filenames for new and old versions
              respectively. You may use *.* instead of listing all directory
              contents. If only one of these parameters is specified, it is
              assumed to be the "old_names" and its contents is compared
              with the content of current directory. If both parameters are
              absent, the default disk and directory are assumed and in 'u'
              mode the program will update current directory contents in
              accordance with already existing comparison protocol. If you
              wish to save your old version, we recommend you to specify
              different directories for old and update versions.

Note: If the file specified in <old_names> does not exist or has been
corrupted, error message is displayed and then the program continues
updating the files following the corrupted one. Error message also
occurs if your old file was compressed by any archiver or was checked
with antivirus utility. You should restore initial state of your files
before using the Upcomp command.

Example:

      UPCOMP C DATA.LST C:\OLD_PCX\*.* C:\NEW_PCX\*.*
This command creates the file with comparison protocol for two catalogs
specified.