An 'Undo' button. See change, +RedoButton.
A file upload field. Example:

    (gui '(+UpField) 30)
Often used together with +Drop. See also +TextField.
A button used scroll a chart one row up. See also chart, +Tiny, +Rid, +JS, +Able +GoButton, +Button and scrolling.
+Upd is a prefix class that can be used to override the upd> method in existing classes. The following example uses +Upd to print updated values to standard error:

    (default *Number 0)

       (html 0 "+Upd" "@lib.css" NIL
          (form NIL
             (gui '(+Upd +Var +NumField)
                '(prog (extra) (msg *Number))
                '*Number 8 )
             (gui '(+JS +Button) "Increment"
                '(inc '*Number) ) ) ) )
Constructs a URL, building it up with session id and an icon. May be used as a prefix class in several, "clickable", classes but is useful by itself too. The following example makes a context clickable:

   (gui '(+View +Url +TextField)
      '(and (port> (: home obj)) (pack "https://foo.net/" @))
      '((Url) (pack Url "/umc/adm.l?*PW=" (pw))) )
See also +HttpField, +MailField, +TelField and +TextField.
(url URL . @)
Can be called in a button action to jump to an arbitrary URL instead of the normal re-display of the current form.

    (gui '(+Rid +Button) "Contemporaries"
       '(url "!contemporaries" (: home obj)) )
See also +Button, +Rid.
Prefix class, converts to upper case.

  "Upper case" (gui '(+Uppc +TextField) 30)
See also +Lowc.