For the purpose of data exchange, Part 21 of the STEP standard specifies architecture for clear text encoded files, known colloquially as a STEP File or a Part 21 File.
A STEP File consists of two sections, a header section and a data section, as illustrated in Example 4.
Example 4: A working example of a STEP File.
Header section
The header section provides information about the nature and the originator of the file. It is enclosed within the keywords HEADER and ENDSEC.
The schema of a STEP File header is illustrated in Example 5.
Example 5: An EXPRESS description of the header section of a STEP File.
Data section
The data section includes description of the entity instances to be exchanged. The data section is enclosed within the keywords DATA and ENDSEC.
Entity instances are presented in the following form (refer also to Example 6):
#<integer value> = <entity name> ( <attribute values> );
Example 6: An instance of the ENTITY Thing in STEP File format.