       emulate [ -R ] [ zsh | sh | ksh | csh ]
              Set  up  zsh options to emulate the specified shell
              as much as possible.  csh will never be fully  emu-
              lated.   If  the  argument is not one of the shells
              listed above, zsh will be used as  a  default.   If
              the  -R  option  is given, all options are reset to
              their default value corresponding to the  specified
              emulation mode.
