touchback - (American football) a play in which the opposing team has kicked the football into your end zone.
From Wikipedia, the free encyclopedia. A check digit is a form of redundancy check used for error detection on identification numbers, such as bank account numbers, which are used in an application where they will at least sometimes be input manually. It is analogous to a binary parity bit used to check for errors in computer-generated data.
Calculating the Check Digit. 1  1. Understand what a routing number is. The routing number is located in the bottom left hand corner of a check. 2  2. Understand the Checksum algorithm. This is the algorithm that is used to validate the authenticity of the routing number. 3  3. Use the Checksum algorithm to find a missing check digit.