Win32: SAL annotation (source-code annotation language)
These are macros that help the compiler check function
In SAL2 they became mixed case:
_In_ // Data is passed to the called funtion (`const`)
_Out_ // The caller only provides space for the called function to write to
_Inout_ // Usable data is passed into the function and potentially is modified.
_Outptr_ // The value that's returned by the called function is a pointer.
There are many others but those are the important ones
__in became _In_
__out became _Out_
__inout became _Inout_
No earlier equivalent of _Outptr