Levels of Data in a Record Description Entry

Each group and elementary item in a record requires a separate entry, and each must be assigned a level-number.

A level-number is a 1- or 2-digit integer between 01 and 49, or one of three special level-numbers: 66, 77, or 88. The following level-numbers are used to structure records:
01
This level-number specifies the record itself, and is the most inclusive level-number possible. A level-01 entry may be either a group item or an elementary item. It must begin in Area A. Type-names (defined using the TYPEDEF clause) must be level-01 items.
02-49
These level-numbers specify group and elementary items within a record. They may begin in Area A or Area B. Less inclusive data items are assigned higher (not necessarily consecutive) level-numbers in this series.

A group item includes all group and elementary items following it, until a level-number less than or equal to the level-number of this group is encountered.

All elementary or group items immediately subordinate to one group item must be assigned identical level-numbers higher than the level-number of this group item.

If a type-name is a group item, and it is used in a TYPE clause to define a new data item, then the new data item will have subordinate items of the same name, description, and hierarchy as those of the type-name. There is no limit to the number of levels that can result because:
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