Understanding CellFormating and How it is stored

I am trying to understand how to extract or even understand how cell formatting is stored. I found that <b/> in the <font> signifies the cell is bold. But how is it stored if several words in the file are bolded and several are not. I need to be able to copy the values and preserve there formatting. Any help will be greatly appreciated.

I put "This is a bold test" in a cell and the shared string entry looks like this:

  <si>
    <r>
      <t xml:space="preserve">This is a </t>
    </r>
    <r>
      <rPr>
        <b/>
        <sz val="11"/>
        <color theme="1"/>
        <rFont val="Calibri"/>
        <family val="2"/>
        <scheme val="minor"/>
      </rPr>
      <t>bold</t>
    </r>
    <r>
      <rPr>
        <sz val="11"/>
        <color theme="1"/>
        <rFont val="Calibri"/>
        <family val="2"/>
        <scheme val="minor"/>
      </rPr>
      <t xml:space="preserve"> test</t>
    </r>
  </si>

The "r" elements are "runs" of text. Each run of text has the same formatting. The "rPr" shows the properties of that run. Any properties set for a run will still apply for other runs unless those properties are replaced by new values. In this example, the word "bold" had a bold font property and then the run for the rest of the text does not have a bold font.

The same type of formatting can also appear in an inline string (is element for a cell with the "inlineStr" type).