Int 2F Fn 1401  - European Ms-dos 4.0 Popup - "postpu" - Open/close Popup  [D]

   AX = 1401h
   DL = function (00h open, 01h close)
   DH = wait flag
       00h block until screen opens
       01h return error if screen is not available
       02h urgent--always open screen immediately

Return: CF clear if successful
       BX = amount of memory needed to save screen and keyboard info,
       0000h if default save location can be used (only if DH was 02h)
   CF set on error

Note:  the application using the screen is frozen until the popup screen is
     closed

See Also: AX=1400h"POPUP",AX=1402h"POPUP",AX=1403h"POPUP"