PROGRAM ZOOMS (INPUT,OUTPUT,GRAPHIC);                       
(* 12.10.1986 FLORIAN MATTHES                        *)     
(* DIESES PROGRAMM IST NUR ZUR DEMONSTRATION DER GRAFIK   *)
(* IM MEHRFARBENMODUS AUF DER DISKETTE VORHANDEN          *)
                                                            
  CONST XMAX  = 159;                                        
        YMAX  = 199;                                        
                                                            
  TYPE  POINT = RECORD                                      
                  X,Y              : INTEGER;               
                END;                                        
                                                            
  VAR   A,B,C,D: POINT;                                     
        FARBE  : 0..3;                                      
        WINKEL : INTEGER;                                   
                                                            
  PROCEDURE GETPOINT(VAR P:POINT);                          
  BEGIN                                                     
   P.X:= INT(XMAX * RANDOM(0));                             
   P.Y:= INT(YMAX * RANDOM(0));                             
  END; (* GETPOINT *)                                       
                                                            
  PROCEDURE ZOOM(COLOR: INTEGER; P1,P2,P3,P4:POINT);        
  (* MUTIERE QUADRAT P1/P2 ZU P3/P4 *)                      
   VAR C: 0..1;                                             
                                                            
    PROCEDURE GROW(VAR FROM:INTEGER; UPTO:INTEGER);         
    BEGIN                                                   
      IF FROM<UPTO THEN FROM:=FROM+1 ELSE                   
      IF FROM>UPTO THEN FROM:=FROM-1;                       
    END; (* GROW *)                                         
                                                            
  BEGIN                                                     
   C:=COLOR;                                                
    REPEAT                                                  
      BOX(C,P1.X,P1.Y,P2.X,P2.Y,WINKEL);                    
      GROW(P1.X,P3.X);                                      
      GROW(P1.Y,P3.Y);                                      
      GROW(P2.X,P4.X);                                      
      GROW(P2.Y,P4.Y);                                      
      C:= COLOR - C;                                        
    UNTIL (P1.X=P3.X) OR (P1.Y=P3.Y);                       
  END; (* ZOOM *)                                           
                                                            
BEGIN                                                       
  COLOR(0,1); COLOR(1,2); COLOR(2,3); COLOR(3,6);           
  COLOR(4,1); COLOR(5,5);                                   
  WRITE("DREHWINKEL? (0-360) :0", #157);                    
  READLN(WINKEL);                                           
                                                            
  GRAPHIC(3,1); FARBE:=1;                                   
  WHILE NOT KEYPRESSED DO                                   
    BEGIN                                                   
      GETPOINT(A); GETPOINT(B);                             
      GETPOINT(C); GETPOINT(D);                             
      ZOOM(FARBE,A,B,C,D);                                  
      IF FARBE=3 THEN FARBE:=1                              
                 ELSE FARBE:= FARBE+1;                      
    END;                                                    
  GRAPHIC(0,1);                                             
END.