Let $\mathscr{C}(\mathbb{R})$ be the set of all the functions from $\mathbb{R}$ to $\mathbb{R}$ which are continuous on $(-\infty, \infty)$, and let $\mathscr{D}(\mathbb{R})$ be the set of all the functions from 2 to $\mathbb{R}$ which are differentiable on $(-\infty, \infty)$. Then $\mathscr{C}(\mathbb{R})$ and $\mathscr{D}(\mathbb{R})$ are subrings of $\mathscr{F}(\mathbb{R})$.