100 REM ROT-13
110 CLS : REM  110 HOME for Applesoft BASIC
120 INPUT "Enter a string: ";a$
130 GOSUB 160
140 PRINT b$
150 END
160 REM FUNCTION rot13
170 FOR i = 1 TO LEN(a$)
180 n = ASC(MID$(a$,i,1))
190 e = 255
200 IF n > 64 AND n < 91 THEN e = 90 : REM uppercase
210 IF n > 96 AND n < 123 THEN e = 122 : REM lowercase
220 IF e < 255 THEN n = n+13
230 IF n > e THEN n = n-26
240 b$ = b$+CHR$(n)
250 NEXT
260 RETURN