A note in a note pad either does or does not have content. A note without content is said to be a null note. A note with content contains a copy of data supplied by the application. The format and content of these data are determined by the requirements and design of the application. The note size is the number of bytes of data that the note contains. Two fixed note sizes are supported, 0 and 1024. A note of size 0 is a null note. A note with content has 1024 bytes of data.

Null notes might be useful in a variety of ways. For example, note content might not be needed at all if some combination of note name, tag value, and perhaps instance number can be used to meet the needs of the application. Alternatively, an application might use a null note to represent some special state such as logically deleted. A null note consumes less space in the note pad than does a note with content. Most applications are likely to need notes with content.

To create a note with content, your program issues a create note request and provides a buffer containing the desired note content. If the note already exists, your program can replace the current note content by providing a buffer containing new content when issuing a replace request (or a write request). If the note was a null note, the replace request (or write request) would cause the note to have content.

To create a null note, your program issues a create request but does not provide any content. If the note already exists, your program can convert the note into a null note by deleting the note content (not the note itself). The note content is deleted by issuing a replace request (or write request), and providing a buffer of length zero.

The IXCNOTE macro provides two different ways of specifying no content. You can either specify the keyword NOBUFFER, or you can specify the keywords BUFFER and BUFLEN with the buffer length set to zero. When creating a note, either specification causes a null note to be created. However, these specifications have different behaviors when replacing an existing note. Issuing a replace note request with NOBUFFER will update the tag value and instance number, but not the note content. Issuing a replace note request with BUFFER and BUFLEN=0 will update the tag value and instance number, and will also delete the note content (which makes it a null note). A write request behaves like a create request if the designated note does not exist, and behaves like a replace request if the note does exist.