what is pdu in android

 
A PDU is a “protocol data unit”, which is the industry format for an SMS message. because SMSMessage reads/writes them you shouldn’t need to disect them. A large message might be broken into many, which is why it is an array of objects.
 
** UPDATE: Android Complete tutorial now available here.
 
PDU, or protocol data unit, refers to one method of sending information along cellular networks. SMS messaging, as described in the 3rd Generation Partnership Project  (3GPP) Specification, supports two different ways of sending and receiving messages. The first is text mode, which some phones don’t support. Text mode encodes message content as a simple bit stream. The other is PDU mode, which contains not  only the SMS message, but also metadata about the SMS message, such as text encoding, the sender, SMS service center address, and much more. To access this metadata, mobile SMS applications almost always use PDUs to encode the contents of a SMS message.