  The approximation of natural numbers subsets has always been one of the
fundamental issues in computability theory. Computable approximation,
$\Delta_2$-approximation, as well as introducing the generically computable
sets have been some efforts for this purpose. In this paper, a type of
approximation for natural numbers subsets by computably enumerable sets will be
examined. For an infinite and non-c.e set, $W_i$ will be an $A$.maximal
(maximal inside $A$) if $W_i \subseteq A$, is infinite and $\forall j (W_i
\subseteq W_j \subseteq A) \to \Delta (W_i, W_j )< \infty$, where $\Delta$ is
the symmetric difference of the two sets. In this study, the natural numbers
subsets will be examined from the maximal subset contents point of view, and we
will categorize them on this basis. We will study c.regular sets that are
non-c.e. and include a maximal set inside themselves, and c.irregular sets that
are non-c.e. and non-immune sets which do not include maximal sets. Finally, we
study the graph of relationship between c.e. subsets of c.irregular sets.
