10 DEF FN S(A)=A*A
20 PRINT FN S(2): REM THIS WILL WORK
30 PRINT FN C(2): REM CALLING A FUNCTION PRIOR TO DEFINITION MAY NOT WORK
40 GOSUB 9000
50 PRINT FN C(2): REM THIS WILL WORK
60 END
9000 DEF FN C(A)=A*A*A
9999 RETURN