100 cls
110 roman$ = "MCMXCIX" : print roman$,"=> "; : gosub 170 : print decimal '1999
120 roman$ = "XXV" : print roman$,"=> "; : gosub 170 : print decimal     '25
130 roman$ = "CMLIV" : print roman$,"=> "; : gosub 170 : print decimal   '954
140 roman$ = "MMXI" : print roman$,"=> "; : gosub 170 : print decimal    '2011
150 end
160 rem Decode from roman
170 decimal = 0
180 predecimal = 0
190 for i = len(roman$) to 1 step -1
200  x$ = mid$(roman$,i,1)
210  select case x$
220   case "M" : n = 1000
230   case "D" : n = 500
240   case "C" : n = 100
250   case "L" : n = 50
260   case "X" : n = 10
270   case "V" : n = 5
280   case "I" : n = 1
290   case else : print "not a roman numeral" : end
300  end select
310  if n < predecimal then decimal = decimal-n else decimal = decimal+n
320  predecimal = n
330 next i
340 return