can't parse this nawk statement

UNIX AIX
1

hi all

i have the following portion in an xml file:

</n:AOMessage>
<?xml version="1.0" encoding="UTF-8"?>
<n:AOMessage xmlns:n="urn:ao:hs:update:shell" xmlns:bo="urn:ao:hs" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:ao:hs:update:shell http://staging.aoschema.ai2.cio.gto.intranet.ao.com/aoxml/HSUpdate/1.0/aoxml.hsupdate.xsd" aoXML.SchemaVersion="1.0">
  <aoXML.BusinessHdr>
    <aoXML.BusinessObjectType>HSUPDATE/INIT</aoXML.BusinessObjectType>
    <aoXML.BusinessObjectOwner>CDNA</aoXML.BusinessObjectOwner>
    <aoXML.BusinessObjectId>ldap:2369586</aoXML.BusinessObjectId>
    <aoXML.BusinessObjectVersion>0</aoXML.BusinessObjectVersion>
    <aoXML.BusinessEventTimeStamp>2010-04-22T17:22:54Z</aoXML.BusinessEventTimeStamp>
    <aoXML.BusinessObjectEventType>NEW</aoXML.BusinessObjectEventType>
    <aoXML.SchemaVersion>1.0</aoXML.SchemaVersion>
  </aoXML.BusinessHdr>
  <HSUpdate status="COMPLETED" type="INIT">
    <OrderIdentity domain="CDNA">1426423-1</OrderIdentity>
    <Timestamp>2010-04-22T17:22:55Z</Timestamp>
    <Value xsi:type="bo:LDAPValueType">
      <AoDirId>2369586</AoDirId>
      <Email>adrianne.lois@ao.com</Email>
      <NotesID>HSLOIS</NotesID>
      <Comments />
    </Value>
  </HSUpdate>
</n:AOMessage>

..which was nawk'd by a one liner command:

nawk 'c-->0;$0~s{if(b)for(c=b+1;c>1;c--)print r[(NR-c+1)%b];print;c=a}b{r[NR%b]=$0}' b=13 a=9 s="`echo ${u}" $PSHOME/ai2/aoadapter-3.16/logs/AOAdapter_PeopleSoft.xml*

can someone help me analyze / break down each part in a way that's more understandable? i'm not a programmer but would love to know more about unix scripting

thanks!