Definition:Kaprekar's Process

Definition
Kaprekar's process is the repeated application of the Kaprekar mapping to a given positive integer.

Also known as
Kaprekar's process is also known as the Kaprekar routine or the Kaprekar sequence.

Also defined as
Some sources define the Kaprekar mapping so as not to retain the leading zeroes, and so, for example:
 * $K \left({1121}\right) = 2111 - 1112 = 999$
 * $K \left({999}\right) = 999 - 999 = 0$

instead of:
 * $K \left({1121}\right) = 2111 - 1112 = 0999$
 * $K \left({0999}\right) = 9990 - 0999 = 8991$

The process as initially specified does retain all leading zeroes.