Weird string preceeding function declaration

[Deathly]

size_t __cdecl wcslen (const wchar_t *) ;

What does __cdec1 mean here? Is this something specific to windows programming? Why doesn't cplusplus reference have wcslen function in it? (it's like strlen in string.h but for wchar_t's)

[Zhuge]

Yes, I'm pretty sure it is a Windows function.

_cdecl stands for "C declaration" or something similar, and represents the calling convention.

http://msdn.microsoft.com/en-us/library/zkwh89ks%28v=VS.100%29.aspx