10 CLS
20 PRINT "The sums of the digits are:" : PRINT
30 B = 10
40 N$ = "1" : GOSUB 100 : PRINT "1    base 10 :" N
50 N$ = "1234" : GOSUB 100 : PRINT "1234 base 10 :" N
60 B = 16
70 N$ = "FE" : GOSUB 100 : PRINT "FE   base 16 :" N
80 N$ = "F0E" : GOSUB 100 : PRINT "F0E  base 16 :" N
90 END
100 REM SUM DIGITS OF N$, B
110 IF B = 1 THEN N = LEN(N$) : RETURN
120 IF B < 2 THEN B = 10
130 N = 0
140 V$ = LEFT$("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ", B)
150 FOR I = 1 TO LEN(N$)
160   C$ = MID$(N$, I, 1)
170   FOR J = 1 TO LEN(V$)
180     IF C$ <> MID$(V$, J, 1) THEN NEXT J : N = SQR(-1) : STOP
190   N = N + J - 1
200 NEXT I
210 RETURN