Section 2.2.7.1.5. Character set

(22) Characters within a CIF are restricted to certain printable or white-space characters. Specifically, these are the ones located in the ASCII character set at decimal positions 09 (HT or horizontal tab), 10 (LF or line feed), 13 (CR or carriage return) and the letters, numerals and punctuation marks at positions 32–126.

Comment: The ASCII characters at decimal positions 11 (VT or vertical tab) and 12 (FF or form feed), often included in library implementations as white-space characters, are explicitly excluded from the CIF character set at this revision.

(23) Comment: The reference to the ASCII character set is specifically to identify characters in an established and widely available standard. It is understood that CIFs may be constructed and maintained on computer platforms that implement other character-set encodings. However, for maximum portability only the characters identified in the section above may be used. Other printable characters, even if available in an accessible character set such as Unicode, must be indicated by some encoding mechanism using only the permitted characters. At this revision, only the encoding convention detailed in Section 2.2.7.4(30)–(37) is recognized for this purpose.