Chgmsgq/rcvmsg

I'm looking into what's really behind these commands. What I'm trying to do
in a clp is just browse through a message queue until I hit the end, do a
delay, and return to the top of the loop to check for any new messages. 
A couple of questions:
- Will chgmsgq msgq(<msgq>) reset(*no) set me at the current last message,
or where is it pointing to in the message list?
- Does a rcvmsg function like a "read" and move the pointer in the message
queue like reading a file sequentially?