The ARINC424 specifies a format of navigation (and communication) data based on text files containing lines of 132 alphanumeric characters. Section 4 “ARINC424 Records” and Section 5 “ARINC424 Fields” detail the textual structure and the type of alphanumeric characters which shall be used in order to represent aeronautical features. The picture below illustrates how an Airport can be expressed in ARINC424.
In addition to the description of the format, the ARINC424 specification also provides a series of rules (Business rules) explaining how the Aeronautical Information Publication should be interpreted (naming convention for waypoints for instance). One of the major chapters of the specification (Attachment 5) deals with the encoding of terminal procedures (SID, STAR, Approaches). The ARINC424 defines in particular the concept of Path&Terminators (elementary trajectories which are sequenced in order to represent a complete procedure) which is now more and more adopted outside the strict A424 community. As an example, the ARINC424 Path&Terminator concept is reused in the ICAO Performance-Based Navigation Manual.