cases simply
by typing the TAB key.  Documentation is in the zshcompsys manual page.
If it is not turned on, only a few simple completions such as filenames
are available but the time to start the shell is slightly shorter.

You can:
  (1)  Turn on completion with the default options.

  (2)  Run the configuration tool (compinstall).  You can also run
       this from the command line with the following commands:
        autoload -Uz compinstall
        compinstall
       if you don't want to configure completion now.

  (0)  Don't turn on completion.
ž