Retaining variables with power off

I'm trying the possibility for the nRF52 to retain RAM contents even in a SYSTEMOFF condition.

However, I have a question regarding the C compiler behavior: Whenever an application starts, are the declared variables initialized to a known condition, even if you don't do it explicitly ?

pjrebordao:
However, I have a question regarding the C compiler behavior: Whenever an application starts, are the declared variables initialized to a known condition, even if you don't do it explicitly ?

How is the compiler supposed to know what the right value is? You should not read from uninitialized variables. The behavior is undefined.