Chapter 2 of the AFP Reference
2. Generated AFP Documents
IREn AFP generator generates documents which are MODCA-P streams that contain PTOCA objects and IOCA objects. IREn AFP generator can also generate an additional stream that can contain some of raster images as IOCA objects. This stream is a MO:DCA-L stream and it is called resource file.
For purpose of interoperability each MO:DCA structured field is prefixed with byte X'5A'. For details on X'5A' prefix usage, see Advanced Function Presentation, Programming Guide and Line Data Reference, Chapter 4. Mixed Documents: Adding MO:DCA Structured Fields to Line Data, Section "X'5A' Carriage Control Character".