By convention, the form-type code for registered form types contains only digits and uppercase letters. Form-type codes that are all uppercase denote a registered, unique form type. Use lowercase letters for temporary or prototype chunk types.
Certain chunk types are also globally unique and must also be registered before use. These registered chunk types are not specific to a certain form type; they can be used in any form. If a registered chunk type can be used to store your data, you should use the registered chunk type rather than define your own chunk type containing the same type of information.
For example, a chunk with chunk ID 'INAM' always contains the name or title of a file. Also, within all RIFF files, file names or titles are contained within chunks with ID 'INAM' and have a standard data format.