text: volatile int pixel_buffer_start; // global variable
  
  int main(void)
  {
      volatile int * pixel_ctrl_ptr = (int *)0xFF203020;
      /* Read location of the pixel buffer from the pixel buffer controller */
      pixel_buffer_start = *pixel_ctrl_ptr;
  
      clear_screen();
      draw_line(0, 0, 150, 150, 0x03);   // this line is blue
      draw_line(150, 150, 319, 0, 0x1C); // this line is green
      draw_line(0, 239, 319, 239, 0xE0); // this line is red
      draw_line(319, 0, 0, 239, 0xED);   // this line is a pink color
  }
  
  // code not shown for clear_screen() and draw_line() subroutines
  
  void plot_pixel(int x, int y, char line_color)
  {
      *(char *)(pixel_buffer_start + (y << 9) + x) = line_color;
  }
  