Level-Numbers

A system of level-numbers shows the organization of elementary items and group items. Since records are the most inclusive data items, level-numbers for records start at 01. Less inclusive data items are assigned higher (not necessarily successive) level-numbers not greater in value than 49. A maximum of 49 levels in a record is allowed. There are special level-numbers, 66, 77

 , 78

and 88 which are exceptions to this rule (see below). Separate entries are written for each level-number used.

A group includes all group and elementary items following it until a level-number less than or equal to the level-number of that group is encountered. All items which are immediately subordinate to a given group item should be described using identical level-numbers greater than the level-number used to describe that group item

 ; this rule is not insisted upon

.

Example

Four types of entries exist for which there is no true concept of level. These are:

1. Entries that specify elementary items or groups introduced by a RENAMES clause.
2. Entries that specify noncontiguous working storage and linkage data items.
3. Entries that specify condition-names.
4.   Entries that specify constant-names.

Entries describing items by means of RENAMES clauses for the purpose of regrouping data items have been assigned the special level-number 66.

Entries that specify noncontiguous data items, which are not subdivisions of other items, and are not themselves subdivided, have been assigned the special level-number 77.

Entries that specify condition-names, to be associated with particular values of a conditional variable, have been assigned the special level-number 88.

  Entries that specify constant-names, to be associated with the value of a particular literal, have been assigned the special level-number 78.

Note that indentation of COBOL source code is a readability convention only and is not part of the language.

Elementary items are by definition those items without any subordinate entries (entries without numerically greater level-numbers) following, and must have a storage definition associated with them (see the topics The PICTURE Clause and the The USAGE Clause).

Note that only elementary items (marked with an asterisk, "*", above) and FILLER items (marked with a "#" sign above) have storage explicitly reserved for them (in accordance with the associated PICTURE clause); non-elementary items have implicit storage associated with them of size determined by their subordinate items plus any FILLER bytes needed for synchronization (see the topic The SYNCHRONIZED Clause).

Level-numbers need not be consecutively ascending or descending as shown above for clarity; thus, the next subordinate level after 01 could be 05, and the next level 10, and so on.

The above data descriptions would produce storage allocation in the following manner:

where: