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Let $R$ be a commutative ring with $1$, if $R$ contains only finitely many ideals, then every nonzero element of $R$ is either a unit or a zero divisor. I know it's true. How about the converse? i.e. If every nonzero element of $R$ is either a unit or a zero divisor, then $R$ contains only finitely many ideals. Is it true? Can you give me an example about a commutative ring with $1$ that has infinitely many zero divisors? Thanks.

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Example: $\mathbb{F}_2^\mathbb{N}$. Everything is $0$, the unit, or a zero divisor. – Daniel Fischer Jul 17 '13 at 19:11
Thanks. Useful example. – Yeyeye Jul 17 '13 at 19:20
up vote 5 down vote accepted

The converse is not true. Consider the ring $R=\mathbb{C}[x,y]/(x^2,y^2,xy)$. Notice that every element has a representative of the form $a+bx+cy$. If $a=0$, this is a zero-divisor. If $a\ne 0$, then $a^{-1}-a^{-2}bx-a^{-2}cy$ is an inverse. So this ring satisfies the hypotheses of the question. Can you exhibit infinitely many ideals of this ring?

$R$ is also an example of an infinite commutative ring with infinitely many zero divisors.

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Thanks. Good example. – Yeyeye Jul 17 '13 at 19:19

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