wn_open -- open window 

        USAGE

          wn = (WINDOWPTR)wn_open(page, row, col, width, height, atrib, batrib)
          int page, row, col, width, height, atrib, batrib;

                page -  0 ,1000, or 800.
                        1000 opens a borderless page
                         800 opens an exploding window
                row  -  row of upper left hand corner of the window
                col  -  column of upper left hand corner of the window
                width - INSIDE dimension (max value is 78, 80 if page = 1000)
                height- INSIDE dimension (max value is 23, 25 if page = 1000)
                atrib - attribute to be used IN the window
                batrib- attribute to be used for the border

          wn_open is usually the first function called to create and use
          a window.  wn_open dynamically allocates memory to save the
          area defined by row, col, width, and height - saves the image,
          opens the window and homes the logical cursor to row 0, col 0
          of the window.  The window is now ready to be used by the
          various window management routines.

          Attributes are defined in windows.h.

        RETURNS

          wn = window handle or NULL if error

        CAUTIONS

          Width and height are inside dimensions. If you want a window
          with a work area of 10 rows and 5 columns, the width is 7 and
          the height is 12.

          The flashing cursor will not be displayed unless wn_sync() has
          been called with a value of TRUE.

          The window "wn" automatically becomes the top window tile upon
          return.