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 Begin buffering screen output

     DISPBEGIN() --> NIL


     DISPBEGIN() always returns NIL.


     DISPBEGIN() is a screen function that informs the CA-Clipper display
     output system that the application is about to perform a series of
     display operations.

     Use DISPBEGIN() with DISPEND() to allow the display output system to
     buffer display updates.  Display output which occurs after DISPBEGIN()
     but before DISPEND() is allowed to accumulate in internal buffers.  When
     DISPEND() executes, any pending updates appear on the physical display.
     This is useful in applications where complex screen displays are slow
     and the appearance of performance is desired.

     DISPBEGIN() and DISPEND() calls are optional.  They are not required for
     normal output.


     .  Nested calls: DISPBEGIN() calls are nested internally.  If
        several DISPBEGIN() calls occur, buffering is allowed until a
        corresponding number of DISPEND() calls occur.

     .  Guaranteed operations: Display updates performed between
        DISPBEGIN() and DISPEND() are not guaranteed to be buffered--some
        updates may become visible before DISPEND() is called.  However, all
        updates are guaranteed to be visible after the closing call to

     .  Terminal operations: Terminal input operations such as INKEY()
        or READ should not be performed between DISPBEGIN() and DISPEND().
        Doing this may cause input or display output to be lost.

     .  Incompatible operations: Display output by other than the
        CA-Clipper display functions (e.g., by add-on libraries or by DOS via
        OUTSTD(), etc.) may not be compatible with DISPBEGIN() and DISPEND().
        Output may be lost.


     .  This example buffers screen output, updates the screen, and
        then displays the buffered screen output:

        DISPBEGIN()            // Start screen buffering
        SETPOS(10, 10)
        DISPOUT("A display update")
        SETPOS(11, 10)
        DISPOUT("Another display update")
        DISPEND()               // Display buffered screen data

 Files   Library is CLIPPER.LIB.

See Also: DISPEND()
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