# Format Identifiers

Property set values are stored in a section that is tagged with a unique format identifier. For example, the FMTID for the OLE Summary Information property set is:

    F29F85E0-4FF9-1068-AB91-08002B27B3D9

To define a FMTID for the Summary Information property set, you would use the DEFINE_GUID macro in an include file for the code that manipulates the property set:

    DEFINE_GUID(FMTID_SummaryInformation, 0xF29F85E0, 0x4FF9, 0x1068,
    0xAB, 0x91, 0x08, 0x00, 0x2B, 0x27, 0xB3, 0xD9);

Anywhere in your code you need to use the FMTID for the Summary Information property set, you can access it through the FMTID_SummaryInformation variable.

When storing property sets in IStorage instances, you need to convert the FMTID to a string name for the storage object.