What is an Ordinal number?

Commonly, ordinal numbers, or ordinals for short, are numbers used to denote the position in an ordered sequence: first, second, third, fourth, etc.
But in the tech world ordinal numbers are exported functions in a module which have a fixed number as opposed to a name associated with it. So how do we make the connection?

How do we find out when I get an error like “ordinal 6928 can not be located in MFC42u.dll” what function is it referring to?

By using the dumpbin utility, which comes with Visual studio.

% dumpbin /exports $dll | findstr $ordinal

 Ex:

% dumpbin /exports mfc42u.lib | findstr 6928

          6928    <?AfxThrowInvalidArgException@@YGXXZ>