There is some debate between my colleague and I about the `U` suffix after hexadecimally represented literals. Note, this is not a question about the meaning of this suffix or about what it does. I have found several of those topics here, but I have not found an answer to my question.

**Some background information:**

We're trying to come to a set of rules that we both agree on, to use that as our style from that point on. We have a copy of the *2004 Misra C* rules and decided to use that as a starting point. We're not interested in being fully Misra C compliant; we're cherry picking the rules that we think will most increase efficiency and robustness.

Rule 10.6 from the aforementioned guidelines states:

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> A “U” suffix shall be applied to all constants of unsigned type.
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> 
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I personally think this is a good rule. It takes little effort, looks better than explicit casts and more explicitly shows the intention of a constant. To me it makes sense to use it for **all** unsigned contants, not just numerics, since enforcing a rule doesn't happen by allowing exceptions, especially for a commonly used representation of constants.

My colleague, however, feels that the hexadecimal representation doesn't need the suffix. Mostly because we almost exclusively use it to set micro-controller registers, and signedness doesn't matter when setting registers to hex constants.

**My Question**

My question is not one about who is right or wrong. It is about finding out whether there are cases where the absence or presence of the suffix changes the outcome of an operation. Are there any such cases, or is it a matter of consistency?

Edit: for clarification; Specifically about setting micro-controller registers by assigning hexadecimal values to them. Would there be a case where the suffix could make a difference there? I feel like it wouldn't. As an example, the Freescale Processor Expert generates all register assignments as unsigned.