[Proj] cs2cs vs. proj??

[Gerald I. Evenden]

A question has arisen in my mind as to what is the difference between the 
programs cs2cs and proj?  What does one do that the other does not?

On the surface the names would imply that one deals with transforming data 
between datum systems, which may include projections as a suboperation, and 
the other would deal with only cartographic projections.

Obviously, as I am painfully aware, this is not the case.

-- 
The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist