A checksum is a type of a simple error detection scheme, meant to catch incorrectly entered data, such as typos. Creditcards, for example, use Luhn algorithm to generate account numbers. Alternatively a checksum number could be a digit appended to the end of data that is being validated.
A super-simple scheme used to validate 6 digit student numbers is as follows:
- Break the number up into 6 digits
- Add up all the digits together to get a new number
- Repeat the process until the result is only a single digit
- Match the resulting digit to the capital letter of alphabet, in that position
123456 1+2+3+4+5+6 = 21 2+1 = 3 3 = C
The input file DATA2.txt will contain 5 lines, 6-digit positive integers, followed by a space and a capital letter. Numbers will not have leading zeros, and thus digits will never add up to 0.
The output file OUT2.txt will contain 5 lines, stating match or error, depending if the number generates the same checksum letter as supplied, or not.
123456 C 123456 A 100000 A 111111 F 111114 I
match error match match match