Incompatible data

Except for the class condition test, the following applies when a data item is referenced in the Procedure Division: If the content of a data item is not compatible with the data class defined for that data item by its PICTURE clause, the result of the operation is undefined.

General rule

1. Every operation involving a numeric data item which may possibly have non-numeric contents (e.g. due to a redefinition of the data item or following a MOVE statement using a group item as operand) should be preceded by the IF NUMERIC class test. The operation can only be performed successfully if the class test yields the truth value TRUE.