Editing COBOL (section)

====Aggregated data====
Data items in COBOL are declared hierarchically through the use of level-numbers which indicate if a data item is part of another. An item with a higher level-number is subordinate to an item with a lower one. Top-level data items, with a level-number of 1, are called ''{{dfn|records}}''. Items that have subordinate aggregate data are called ''{{dfn|group items}}''; those that do not are called ''{{dfn|elementary items}}''. Level-numbers used to describe standard data items are between 1 and 49.{{sfn|ISO/IEC JTC 1/SC 22/WG 4|2014|loc=§ 8.5.1.2}}{{sfn|Cutler|2014|loc=Appendix A}}

<syntaxhighlight lang="cobol">
       01  some-record.                   *> Aggregate group record item
           05  num            PIC 9(10).  *> Elementary item
           05  the-date.                  *> Aggregate (sub)group record item
               10  the-year   PIC 9(4).   *> Elementary item
               10  the-month  PIC 99.     *> Elementary item
               10  the-day    PIC 99.     *> Elementary item
</syntaxhighlight>

In the above example, elementary item {{code|num}} and group item {{code|the-date}} are subordinate to the record {{code|some-record}}, while elementary items {{code|the-year}}, {{code|the-month}}, and {{code|the-day}} are part of the group item {{code|the-date}}.

Subordinate items can be disambiguated with the {{code|IN}} (or {{code|OF}}) keyword. For example, consider the example code above along with the following example:
<syntaxhighlight lang="cobol">
       01  sale-date.
           05  the-year       PIC 9(4).
           05  the-month      PIC 99.
           05  the-day        PIC 99.
</syntaxhighlight>

The names {{code|the-year}}, {{code|the-month}}, and {{code|the-day}} are ambiguous by themselves, since more than one data item is defined with those names. To specify a particular data item, for instance one of the items contained within the {{code|sale-date}} group, the programmer would use {{code|the-year IN sale-date}} (or the equivalent {{code|the-year OF sale-date}}). This syntax is similar to the "dot notation" supported by most contemporary languages.