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 argu-
              ments 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 func-
              tion as a standalone application  if  specified  on
              the  command  line, but merely load in and not exe-
              cute if loaded during an interactive invocation  of
              Tcl.

       auto_path
              Path  to search to locate Tcl scripts.  Used by the
              auto_load command and the TclX unknown command han-
              dler.  The path is a Tcl list of directory names.

       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
              what your doing.