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  SCROLL

  .  Summary

  scroll(int <x>, int <y>, int <x2>, int <y2>, int <lines>, int
  <color>);

  .  Description

  The scroll function is used to scroll or clear a region of the
  screen. The area to handle is defined by <x>,<y> as the upper left
  corner, and <x2>,<y2> as the lower right corner (the upper left cor-
  ner of the screen is 0,0). If the <lines> parameter is a positive
  value, text within the region is scrolled up that many lines. If
  <lines> is a negative value, text within the region is scrolled down
  that many lines. If <lines> is equal to 0, the entire region is
  cleared. Empty lines scrolled into the region will have a color of
  <color>.

  Possible colors are numbered as follows:

                      Black          00
                      Blue           01
                      Green          02
                      Cyan           03
                      Red            04
                      Magenta        05
                      Brown          06
                      Light Grey     07
                      Dark Grey      08
                      Light Blue     09
                      Light Green    10
                      Light Cyan     11
                      Light Red      12
                      Light Magenta  13
                      Yellow         14
                      White          15

  To obtain a color attribute value for a color combination, the for-
  mula is

       color attribute value =

             foreground color value + (16 * background color value)

  Therefore, a Yellow character on a Blue background would have a
  color attribute value of 30 (14 + (16 * 1)).

  .  Return Value

  None.

  .  Example

  scroll(0, 0, 79, 24, 10, 7);      // scroll screen up 10 lines