title: What does COS stand for?
body: <p>I've been introducing myself to the PDF file structure and have been reading things like:</p>
  
  <ul>
  <li><a href="https://www.adobe.com/devnet/pdf/pdf_reference.html" rel="noreferrer">The Adobe PDF 32000-1:2008 Reference</a></li>
  <li><a href="https://blog.idrsolutions.com/2013/01/understanding-the-pdf-file-format-overview/#helloworld" rel="noreferrer">IDR Solutions Blog</a></li>
  <li><a href="https://web.archive.org/web/20141010035745/http://gnupdf.org/Introduction_to_PDF" rel="noreferrer">GNU Introduction to PDF</a></li>
  </ul>
  
  <p>Then I've come across products such as:</p>
  
  <ul>
  <li><a href="https://www.pdfscripting.com/products/item7.cfm" rel="noreferrer">COS Level Editor for PDF</a></li>
  <li><a href="http://www.windjack.com/product/pdfcanopener/" rel="noreferrer">PDF 'COS level' CanOpener</a></li>
  </ul>
  
  <p>that "<em>display and edit the internal COS(Object) structure of PDF files</em>".</p>
  
  <p>As much as it's obvious what COS Objects are (see section 7.3 of the PDF spec), I can't find any reference or explanation as to what COS is an acronym for.</p>
  
  <p>Does anyone know where the word COS, in relation to PDF, came from?</p>