ROSTER OR TABULATION METHOD -
In this form we define a set by actually listing its elements. For example, the elements in the set A of letters of the English alphabet can be listed as A = {a, b, c,………………,z}. The set of whole numbers is {0, 1, 2, 3, 4, 5,…………………………..}
Note – We do not list an element more than once in a given set. Thus {b, a, l} and not {b, a, l, l} denotes the set of different letters in the word ‘ball’. Also, {l, a, b} defines the same set as {b, a, l}. When listing the members of a set, the name of a member is listed only once, and the members can be written in any order.
Your second block of text...