HEIDENHAIN ITNC 530 - 6-2010 DIN-ISO PROGRAMMING User Manual page 101

File names
When you store programs, tables and texts as files, the TNC adds an
extension to the file name, separated by a point. This extension
indicates the file type.
PROG20 .H
File name File type
File names should not exceed 25 characters, otherwise the TNC
cannot display the entire file name. The following characters are not
permitted in file names:
. ! " ' ( ) * + / ; < = > ? [ ] ^ ` { | } ~
The space (HEX 20) and delete (HEX 7F) characters are not
permitted in file names, either.
The maximum limit for the path and file name together is
83 characters (see "Paths" on page 103).
HEIDENHAIN iTNC 530 101