COBOL Manual for TNS/E Programs (H06.08+, J06.03+)

Neither an index-name nor an index data item can be compared with any operand other than
those mentioned in the preceding rules.
• National Data Items and National Literals
A national data item or a national literal can be compared only to another national data item
or a national literal.
The first three simple relation conditions in Example 67 are equivalent.
Example 67 Simple Relation Conditions
I + 1 > HIGH-I
(I + 1) > HIGH-I
HIGH-I < (I + 1)
TAXABLE-INCOME GREATER THAN ZERO
LAW-NAME = "MURPHY"
"POOL" NOT EQUAL TROUBLE-SOURCE
A-INDEX NOT > 23
Relation Conditions With Nonpointer Operands
subject, object
is an identifier, a literal, an arithmetic expression, an index-name.
relationship
268 Procedure Division