Concept:
The set
\[
R=\{0,1,2,3\}
\]
with addition and multiplication modulo \(4\) is the ring of integers modulo \(4\), denoted by
\[
\mathbb{Z}_4
\]
Step 1: Check ring structure.
Under addition modulo \(4\), \(\mathbb{Z}_4\) is an abelian group.
Under multiplication modulo \(4\), multiplication is associative and distributive over addition.
Thus,
\[
\mathbb{Z}_4
\]
is a ring.
Step 2: Check whether it is an integral domain.
An integral domain has no zero divisors.
But in \(\mathbb{Z}_4\),
\[
2\neq 0
\]
and
\[
2\cdot 2=4\equiv 0\pmod 4
\]
So \(\mathbb{Z}_4\) has zero divisors.
Therefore, it is not an integral domain.
Step 3: Check whether it is a field.
Every field is an integral domain.
Since \(\mathbb{Z}_4\) is not an integral domain, it is not a field.
Step 4: Final answer.
\[
\boxed{\text{a ring}}
\]