title: what is the actual type of streamsize,streamoff and other stream related data type
body: <p>when i want to find out the actual data type of streamsize,the cpp reference says</p>
  <blockquote>
  <p>Type to represent sizes and character counts in streams.</p>
  <p>It is a typedef of one the fundamental signed integral types.</p>
  <p>It is convertible to/from streamoff.</p>
  </blockquote>
  <p>It confused me,and the explanations of other types like streamoff,streampos,fpos are similar.</p>