If you suspect that your program is trying to perform arithmetic on nonnumeric data or is receiving the wrong type of data on an input record, use the class test (the class condition) to validate the type of data.
You can use the class test to check whether the content of a data item is ALPHABETIC, ALPHABETIC-LOWER, ALPHABETIC-UPPER, DBCS, KANJI, or NUMERIC. If the data item is described implicitly or explicitly as USAGE NATIONAL, the class test checks the national character representation of the characters associated with the specified character class.
related references
Class condition (Enterprise COBOL Language Reference)