       The  following  variables  are  set and/or used by the Tcl
       shell.

       argv0  Contains the name of the Tcl program  specified  on
              the command line or the name that the Tcl shell was
              invoked under if no program  was  specified.   argc
              Contains a count of the number of argv arguments (0
              if none).  argv A  list  containing  the  arguments
              passed   in   from   the  command  line,  excluding
              arguments used by the Tcl shell.  The first element
              is the first passed argument, not the program name.

       tcl_interactive
              Set to 1 if Tcl shell is invoked interactively,  or
              0  if the Tcl shell is directly executing a script.
              Normally  checked  by  scripts  so  that  they  can
              function  as  a standalone application if specified
              on the command line, but merely  load  in  and  not
              execute  if loaded during an interactive invocation
              of Tcl.

       auto_path
              Path to search to locate  Tcl  autoload  libraries.
              Used   by   the  both  the  Tcl  and  TclX  library
              autoloading facility.

       tclx_library
              Path to the TclX runtime library.  If your  running
              the  TclX shell or an application based on it (like
              wishx).  The TclX initialization file normally adds
              this to the auto_path.

       tkx_library
              Path  to the TkX runtime library.  This is set only
              if your application has called Tkx_Init.   The  TkX
              initialization  file  normally  adds  this  to  the
              auto_path.

       tcl_prompt1
              Contains code to run to output the prompt used when
              interactively prompting for commands.

       tcl_prompt2
              Contains code to run to output the prompt used when
              interactively  prompting  for  continuation  of  an
              incomplete command.

       TCLXENV
              Array  that contains information used internally by
              various Tcl procedures that are part  of  the  TclX
              shell.   Don't  change  this  array unless you know
