Official Description
6.10 The execution of any action, operation, defined to operate on a variable, is an error if the variable is a program-parameter and, as a result of the binding of the program-parameter, the execution cannot be completed as defined.
Simplified Description
In other words, it is an error to use a program-parameter in a way that is not allowed because of its binding to an external entity.
Error Handling
The bindings of program parameters used by Irie Pascal do not prevent their use in any way and so this error can not occur.