Row-cell <-> 'character codes'

[Jan <jan jan anorak org uk>]

I'm quite new to this list, so maybe what I ask is blindingly obvious
(though I have checked the archives without find an answer).

How do I convert between the row-cell notation (used eg. in Ken Lunde's
book 'CJKV ...') and the numerical values that I see in a hexdump of eg.
a GB18030 encoded text file?

What I am thinking of is NOT whether there is a program that can do it
for me - I actually need to be able to look at the values in a hexdump
and compare them with the entries in the tables in Lunde's book. But he
doesn't seem to mention this subject other than extremely superficially.
This is unfortunately useless for me.

/jan