Notes on the SCR format
=======================

All SCR screen sizes are 720x236 
All SCR file sizes are 22800K - (Scr files have no headers so filesize
                                can be used as filetype recognition)

The image is made up from blocks of eight pixels by eight pixels
and move as follows:
                    

    1  |   2   |  ...  |  90   |   
-------|-------|-------|-------|---------
********       ****    ****    *               
******** ******|   ****|   *****
********       ****    ****    *
**(1)*** (2)   | (..)  | (90)  *   1            
******** *     |       |       |                
******** ***   |       *       |                
******** ***** |       ***     |                
********---****|-------*****---|--------
       |    ******     ********|               
       |   *****       *****   |
       | ***** |       ***     |
  (91  | (92)  | (..)  * (180) |   2              
       | **    |       |       |                
       | *     |       |       |                
       |       |       |       |                
-------|-------|-------|-------|--------


              * = 1 pixel 


The SetLine and Draw commands are used because they are faster than splitting
each byte into 8 bits and ploting the image pixel by pixel, as can be
demonstrated by comparing:


               Scr.Amos      (Setline - Fast) 
          with 
               Scr_Old.Amos  (Plot    - Slow)


If you have trouble understanding how SetLine works try to 
understand how Scr_Old.Amos works first.