Application Guide

494 Getting Started with the Program Editor
Note: When possible, declare as local any variable that is used only within the program
and does not need to be available after the program stops.
What Causes an Undefined Variable Error Message?
An Undefined variable error message is displayed when you evaluate a user-defined
function or run a user-defined program that references a local variable that is not
initialized (assigned a value).
For example:
Define fact(n)=Func
Local mÀ
While n>1
n¦m&m: n–1&n
EndWhile
Return m
EndFunc
À
Local variable m is not assigned an initial value.
Initialize Local Variables
All local variables must be assigned an initial value before they are referenced.
Define fact(n)=Func
Local m: 1&mÀ
While n>1
n¦m&m: n–1&n
EndWhile
Return m
EndFunc
À
1 is stored as the initial value for m.
Note (CAS): Functions and programs cannot use a local variable to perform symbolic
calculations.
CAS: Performing Symbolic Calculations
If you want a function or program to perform symbolic calculations, you must use a
global variable instead of a local. However, you must be certain that the global variable
does not already exist outside of the program. The following methods can help.
• Refer to a global variable name, typically with two or more characters, that is not
likely to exist outside of the function or program.
• Include DelVar within a program to delete the global variable, if it exists, before
referring to it. (DelVar does not delete locked or linked variables.)