Specifying Subfield Length
The length of a subfield may be specified using absolute (positional)
or length notation, or its length may be implied.
- Free-form
- The length is specified as a parameter to the data-type keyword.
- Absolute notation in fixed form
- Specify a value in both the From-Position (positions 26 through 32) and the To-Position/Length (positions 33 through 39) entries on the definition specification.
- Length notation in fixed form
- Specify a value in the To-Position/Length (positions 33 through 39) entry. The From-Position entry is blank.
- Implied Length
- If a subfield appears in the first parameter of one or
more OVERLAY keywords, the subfield can be defined
without specifying any type or length information. In this case, the
type is character and the length is determined by the overlaid subfields.
In addition, some data types, such as Pointers, Dates, Times and Timestamps have a fixed length. For these types, the length is implied, although it can be specified in fixed form.
When the POS keyword is not specified in a free-form definition, or the From-Position is not specified in a fixed-form definition, the subfield is positioned such that its starting position is greater than the maximum ending position of all previously defined subfields. For examples of each notation, see Data Structure Examples.