  (abridge version) The evolution of population III stars (Z=0) is followed
from the pre-main sequence phase up to the AGB phase for intermediate-mass
stars and up to C ignition in more massive stars...We find that, thanks to the
development of mixing episodes (carbon injections) at the beginning of the AGB
phase, the carbon abundance of the 1, 1.5, 2, 3, 4 and 5Mo models is
significantly increased in the envelope. This process then allows low- and
intermediate-mass stars to achieve a ``standard'' thermally pulsing AGB
phase... In the 7Mo model, the CNO envelope abundance following the second
dredge-up is so large that the star does not experience the carbon injection
episode and follows a more standard thermally pulsing AGB evolution. Our
computations also indicate that, thanks to a small overshooting at the base of
the convective envelope, the third dredge-up is already operating in stars with
M >~1.5 Mo after a few pulses, and that by the end of our modeling, hot bottom
burning is activated in stars more massive than ~ 2Mo. This evolutionary
behavior suggests that primordial low- and intermediate stars could have been
significant contributors to the production of primary 12C, 14N, and may have
contributed to some extent to the production of Mg and Al and possibly
s-elements (despite the lack of iron seeds) in the early universe.
