We began our study of abstract algebra very concretely, by looking at the group Z
of integers, and the related groups Zn. We discovered that each of these groups is
generated by a single element, and this motivated the denition of an abstract cyclic
group. In this section, Theorem 3.5.2 shows that every cyclic group is isomorphic
to one of these concrete examples, so all of the information about cyclic groups is
already contained in these basic examples.