We introduce the notion of `Ring' in this lecture and talk about some standard examples:
1. Rings of integers, rational numbers, real numbers and complex numbers
2. Ring of Gaussian integers, more generally R[a], where R is a subring of B and a is in B
3. Rings of matrices, Hamiltonian quaternions
4. Modulo classes of integers
5. Product of rings
6. Rings of functions
