Meaning of __in , __out, __in_opt

[rup]

What is the meaning of these keywords used before variables in a
function parameters?

__in
__out
__in_opt

 

[jacob navia]

What is the meaning of these keywords used before variables in a
function parameters?

__in
__out
__in_opt

These are Microsoft extensions that annotate the parameters for

__in: input parameter
__out output parameter
__in_opt: optional input parameter

 

[CBFalconer]

What is the meaning of these keywords used before variables in a
function parameters?

__in
__out
__in_opt

They are reserved for the implementor. So read your compiler
documentation. We have no idea.

 

[Tor Rustad]

What is the meaning of these keywords used before variables in a
function parameters?

__in
__out
__in_opt

Sure there wasn't an __inout there too?

I use my own IN, OUT and INOUT macros, to document flow:

#define IN
#define OUT
#define INOUT

Identifiers with "__" prefix, is reserved by your implementation, i.e.
are *not* keywords in C.