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 qscrolldown                                                           QWIKC
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 Function       Scrolls a rows-by-columns block down on the current screen
                and clears the top row of the block.
 Syntax         void qscrolldown( unsigned char row, unsigned char col,
                                  unsigned char rows, unsigned char cols,
                                  int blankattr );
 Remarks        To keep it simple, the block encompasses all affected rows
                including the row to be cleared.  The upper left corner of
                the block starts at (row,col) and the block size is rows by
                cols.  The bottom row will be scrolled out and lost while
                the top row will be cleared with the attribute of blankattr
                (SAMEATTR is permitted).  Note that you can even change 1
                row and/or 1 column.  The cursor is not moved, but is ready
                to be moved with gotoeos.  The cpuid lets the routine choose
                the best speed.
 Return value   None.
 Screens        All video pages and virtual screens.
 EOS            Updated to first cleared column of the cleared row.
 Restrictions   Stay within the screen limits.
 Example        To scroll down the entire screen and clear the top row with
                light cyan on blue:

                  qscrolldown( 1,1, crt_rows, crt_cols, LIGHTCYAN+BLUE_BG );