``` 9000 DEF FN c(n)=n*n*n ``` which sets up the user defined function **FN c(n)** which returns the *cube* of *n* (the number you type into the parentheses). Now exit from *NextBASIC* and return to the calculator – you can now use this user defined function as if it were one of the ZX Spectrum Next's own built-in functions. For example, enter: ``` FN c(3) ``` and the calculator will print the number **27** (i.e. the *cube of 3*). ### Exiting from the calculator When you have finished using the calculator, press the **EDIT** key. The screen will change to:  ``` Options < 14MHz Calculator 32/64/85 Exit 1792K Calculator ``` *Fig. 55 – Calculator Options Menu* Select the *Exit* option to return to the opening menu. If you were working on a *NextBASIC* program before you started using the calculator, then you may return to the program by selecting the *NextBASIC* option. (If you wish to continue using the calculator, then select the *Calculator* option).