z/OS Language Environment Programming Guide for 64-bit Virtual Addressing Mode
SA38-0689-00
The programming_language can be used by the driver program to
determine the format of the parameter list specified on a call_main,
for those cases where the language of the routine associated with
ceexptbl_index is not known.
When a PreInit table entry contains multiple languages, programming_language
is the language of the entry point for the entry.