Check Character Mapping Tool

How Check Character Mapping Tool Works?

The Check Character Mapping Tool works by mapping each numeric check value to an output character through a configurable table, such as 10 → X for ISBN-10 or remainder 14 → Z for the Spanish NIF.

1. 1Enter the range of check values (for example 0–10 or 0–22).
2. 2Assign an output character to each value.
3. 3Mark values that are not allowed (for example 10 in the NHS number).
4. 4Apply the mapping to calculated check values.
5. 5Export the mapping table.

Check Character Mapping Tool Formula

The mapping rule is Check character = M[value], where M is the scheme's lookup table.

Check character = M[v],  v ∈ {0, …, m − 1}
M[v] = ⊥ → payload rejected

• M is the mapping table.
• ⊥ marks a forbidden value.

Check value = 10
M[10] = X
ISBN-10 = 0-8044-2957-X

Check Character Mapping Tool Conversion Table

The mapping table compares how 6 schemes write the extra values above 9.

Schemes such as Spanish NIF (23 letters) and Finnish HETU (31 characters) map every value through a full alphabet.

What is Check Character Mapping Tool?

A Check Character Mapping Tool is a tool that defines how numeric check values become printed characters. Modulus 11 and larger moduli produce values that a single decimal digit cannot hold.

The mapping step is where most implementation bugs appear, such as writing 10 instead of X or forgetting the 11 → 0 rule.

What are the uses of Check Character Mapping Tool?

There are 3 main uses of the Check Character Mapping Tool, including scheme setup, bug fixing, and documentation.

• Scheme setup: Teams define output characters for custom schemes.
• Bug fixing: Developers check mapping edge cases (10, 11).
• Documentation: Specification writers publish the full value table.