The POINTER keyword is used in a free-form definition to indicate that the item has type basing pointer or type procedure pointer.
It must be the first keyword.
The parameter is optional. If the parameter is specified, it must be *PROC, indicating that the item is a procedure pointer.
If the parameter is not specified, the item is a basing pointer.
DCL-S userspace POINTER;
DCL-S callback POINTER(*PROC);
