Ordinal data type
In computer programming, an ordinal data type is a data type with the property that its values can be counted. That is, the values can be put in a one-to-one correspondence with the positive integers. For example, characters are ordinal because we can call 'A' the first character, 'B' the second, etc. The term is often used in programming for variables that can take one of a number of values. While the values are often implemented as integers they are assigned literal names and the programming language can enforce that variables only be assigned those literals.
For instance in Pascal, one can define:
var
x: 1..10;
y: 'a'..'z';
