
Suppose an operator types a US Bank check code into a machine and transposes two adjacent digits (i.e. swaps the
order of two adjacent digits) for example the operator types a3a2 instead of a2a3, will the machine pick up
every error of this type? Does the same apply to ISBN numbers; will a machine detect transposition errors in these numbers?
US Bank check codes are nine digit identification numbers a1a2¼a9 using the digits 0 to 9 where
7a1 + 3a2 + 9a3 + 7a4 + 3a5 + 9a6 + 7a7 + 3a8 º a9 mod 10.
ISBN Numbers have ten digits a1¼a10 using the digits 0 to 9 where
10a1+9a2+8a3+¼+3a8+2a9+a10 º 0 \mod 11.