On systems where file names customarily include an extension signifying file type, the extension “.pna” is recommended for PNA files. Lowercase “.pna” is preferred if file names are case-sensitive.
If PNA archive is split, to facilitate determining the order, insert “.part[n]” before the extension is recommended. The “[n]” part starts from 1 and increases by 1 each time it is split. For example, when an archive is split into two, it will be “.part1.pna” and “part2.pna”. On systems where file names customarily do not include an extension signifying file type, It is recommended to use this instead of the extension. Lowercase is preferred if file names are case-sensitive.