Conditional expressions identify conditions that are tested to enable selection between alternate paths of control depending upon the truth value of the condition. Conditional expressions are specified in the
IF, PERFORM and SEARCH statements. Two categories of conditions are associated with conditional expressions: simple conditions and complex conditions. Each can be enclosed within any number of paired parentheses, in which case its category is not changed.
If the OSVS Compiler directive is set, reference modification cannot be used within a conditional expression.