Kwok,
You've posted a number of questions about this, and have been pointed at the Nios II Processor Reference Handbook, table 3-1. The terms used in this table global pointer, caller saved registers etc. are standard terms, a quick use of google will tell you what they mean.
I suggest you either compile up some C code using the -S option which will produce some assmebler for you to look at, or write your code in C.
