HP 50g Saving variable

[wojtek]

(06-02-2016 05:15 AM)cyrille de brébisson Wrote:  Hello,
Is your HP50 in RPN mode?
Do you have something on stack level 2 before pressing STO?
Is what you have on level 2 not a copy of what you have on level 1 (the name of the variable twice)?
Cyrille

It's in RPN, the message on the LCD says that argument is missing.
But, if I put a name twice on the stack, for example:
'XXX'
'XXX'
and then press STO an error "circular reference" is displayed.
If I enter on the stack
'YYY'
'XXX'
and then press STO, a name 'YYY' will be stored in variable XXX.
The question is: why "circular reference"? Is a value evaluated before storing? Probably not as:
'SIN(30)'
'XX'
STO
saves 'SIN(30)' in variable XX and not just 0.5.