Kreuzworträtsel Betriebssytem

Complete the crossword, then click on "Check" to check your answer. If you are stuck, you can click on "Hint" to get a free letter. Click on a number in the grid to see the clue or clues for that number.
1     2   3                
                  
  4        5            
                  
    6                
                  
            7        
8                    
                  
           9         
                  
 10         11            
                  
     12            13    14   
    15          16        
           17         
   18                 
                  
19         20