Works exactly like the MFC macro TRACE, which itself provides functionality similar to the printf function by sending a formatted string to a dump device such as debug monitor.
Specifies a variable number of arguments that are used in exactly the same way that a variable number of arguments are used in the run-time function printf.
Like printf for C programs under MS-DOS, the ISAPITRACE macro is a convenient way to track the value of variables as your program executes. In the Debug environment, the ISAPITRACE macro output goes to the Debug window of Visual C++. In the Release environment, it does nothing.
ISAPI applications do not have to use MFC. If MFC is not linked to your application, ISAPITRACE provides the same TRACE functionality. If your application is linked to the MFC, ISAPITRACE simply calls MFC's TRACE.