The name is enclosed in slashes and is optional in nested structures only.
If slashes are present, a name must be present.
You can specify the field-list within nested structures only.
There must be at least one field-declaration.
Each structure-name must be unique among structures, although you can use structure names for fields in other structures or as variable names.
The only statements allowed between the STRUCTURE statement and the END STRUCTURE statement are field-declaration statements and PARAMETER statements. A PARAMETER statement inside a structure declaration block is equivalent to one outside.