HEIDENHAIN ITNC 530 - 6-2010 DIN-ISO PROGRAMMING User Manual page 560

17.12 Selecting the Programming
Language for $MDI
Application
The Program input MOD function lets you decide whether to program
the $MDI file in HEIDENHAIN conversational dialog or in ISO format.
To program the $MDI.H file in conversational dialog,
set the Program input function to HEIDENHAIN
To program the $MDI.I file according to ISO,
set the Program input function to ISO
560 MOD Functions