You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allpages apcontinue="Dokumentace_k_wiki.oldcomp.cz" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="570" ns="0" title="BASIC 1Z-016" />
      <p pageid="581" ns="0" title="BGD" />
      <p pageid="476" ns="0" title="Binární soubory" />
      <p pageid="576" ns="0" title="Boot soubory" />
      <p pageid="101" ns="0" title="C-Lab Falcon" />
      <p pageid="10" ns="0" title="Commodore 8bit" />
      <p pageid="104" ns="0" title="Commodore 8bit hardware" />
      <p pageid="143" ns="0" title="Commodore 8bit software" />
      <p pageid="146" ns="0" title="Commodore 8bit zajímavé odkazy" />
      <p pageid="165" ns="0" title="Disketové mechaniky" />
    </allpages>
  </query>
</api>