These are errata and addenda for the book
"A Course in Computational Algebraic Number Theory" 
by Henri Cohen
Graduate Texts in Mathematics 138, Springer-Verlag, 1993, XXI + 534 pages.
ISBN 3-540-55640-0 Springer-Verlag Berlin Heidelberg New York
ISBN 0-387-55640-0 Springer-Verlag New York Berlin Heidelberg

You can get the AmsTeX file errata.tex, the dvi file or the Postscript
file.