A predefined macro called DEFINE_GUID is used to define IIDs as variables in your code.
Microsoft provides a tool called guidgen to generate IIDs and DEFINE_GUID macros.
Guidgen will generate a DEFINE_GUI macro for you. Click the New GUID button to generate a new GUID.
Click the Copy button to copy the DEFINE_GUID macro with the generated IID copied into the clipboard.
Paste the DEFINE_GUID macro into your code. Replace <<name>> with the interface name. For example: