# Undefined variables

**URL:** <https://fortran-lang.discourse.group/t/undefined-variables/3708>\
**Category:** Help\
**Created:** [June 10, 2022, 6:30am UTC](https://fortran-lang.discourse.group/t/undefined-variables/3708 "2022-06-10T06:30:16Z")\
**Posts on this page:** 1\
**Showing post:** 12

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**Author:** ![FortranFan](https://avatars.discourse-cdn.com/v4/letter/f/96bed5/32.png) [@FortranFan](https://fortran-lang.discourse.group/u/FortranFan)\
**Post date:** [June 10, 2022, 2:36pm UTC](https://fortran-lang.discourse.group/t/undefined-variables/3708/12 "2022-06-10T14:36:01Z")

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> [@lkedward](#):
>
> `x1` and `x2` by contrast are on the stack

Not to forget the Fortran language standard does not get into implementation details and considerations such as variables on the stack vs heap are not relevant to the standard.

The key aspect is **undefined**.and per the standard, it makes it nonconforming to reference an object that is undefined.

The instructions with `PRINT` on lines 5, 6, and 7 in the original post thus do not conform and the program behavior can be viewed as `processor-dependent` or better yet, not to be “read much into”.

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