An HL7 message consists of one or more segments. A carriage return character \r (which isĀ 0D in hexadecimal) separates one segment from another. Each segment is displayed on a different line of text.

A segment consists of one or more fields. A pipe character | is used to separate one field from another. If a field contains other fields, the subfields are separated by caret characters ^.

Data types define the kind of data that can be included in a field. For example, a string, formatted text, timestamp, address, or coded element.