rPr element inside pPr element

Hello all. First I want to apologize, if this question is already answered, but I haven't found it :-( I have problem to understand meaning of this:
<w:p>
<w:pPr>
  <w:rPr>
    <w:b/>
  </w:rPr>
</w:pPr>
<w:r>
  <w:t>A</w:t>
</w:r>
</w:p>
This is just fragment of the document. I don't understand what is rPr element inside pPr doing... First I thought, that it sets properties for all runs inside actual paragraph. But it don't. Example above does not print bold letter "A", just normal "A". What's that feature for? Thanks.

It is not for all runs inside paragraph, but paragraph mark.

Find explanation from spec (2.3.1.29 ):

The paragraph glypg's formatting is stored in the rPr element under the paragraph properties(pPr), since there is no run saved for the paragraph mark itself. The paragraph glypg is used to represent the physical location of the paragraph mark for this paragraph.

Besides, OpenXmlClassesExplorer is a good tool for looking up schema element/SDK class definition in a easier way compared to searching in spec.

Hope this helps.

Thanks for the answer. Just one more question. OpenXmlClassesExplorer is just for Open XML Format SDK? Or is it useful for alternative way of developing, too?

I think it's a helper when you develop a complicated solution using sdk, in particular it tells you where are you in the Dom tree, but it can't produce code for you.

btw, could you tell me how long have you been working with Open Xml File Format and the SDK? and what kind of solution are you working on?(just play with it or a biz solution, if biz solution, which industry and the number of target users). appreciate your time and efforts:)

Thanks for this explanation goodol!