10 CLS
20 PRINT "GREATEST COMMON DENOMINATOR" 
30 PRINT 
40 PRINT "(ENTER 0,0 TO END PROGRAM)" 
50 PRINT "ENTER TWO NUMBERS"; 
60 INPUT A,B 
70 IF A<>0 THEN 100  
80 IF B<>0 THEN 100  
90 GOTO 190  
100 A=-ABS(A) 
110 R=A-B*INT(A/B)
120 IF R=0 THEN 160  
130 A=B 
140 B=R 
150 GOTO 110  
160 PRINT "G.C.D:";B 
170 PRINT 
180 GOTO 50   
190 END