121 CHANGED: SET TYPEAHEAD
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     1. Minimum setting:  The minimum setting for SET TYPEAHEAD is
        driver dependent.  For the standard IBM-PC drivers, this minimum
        is 15.  Note, however, that SET TYPEAHEAD TO 0 is a special case
        that is supported for all drivers and that the behavior of SET
        TYPEAHEAD TO 0 is slightly different than in Summer '87.

     2. SET TYPEAHEAD TO 0:  When TYPEAHEAD is SET TO zero, keyboard
        polling is suspended.  An explicit request for keyboard input,
        however, will temporarily enable the keyboard and read any
        pending keystrokes from the BIOS buffer.  Calling NEXTKEY()
        constitutes such an explicit request.  NEXTKEY() reads any
        pending keystrokes from the BIOS buffer and returns the INKEY()
        value of the first keystroke read, or zero if no keystrokes are
        pending.