The destination of the diagnostic message depends on the type of application that called the routine. Console applications receive the message through **stderr**. In a Windows-based application, `assert` calls the Windows [MessageBox](/windows/win32/api/winuser/nf-winuser-messagebox) function to create a message box to display the message with three buttons: **Abort**, **Retry**, and **Ignore**. If the user clicks **Abort**, the program aborts immediately. If the user clicks **Retry**, the debugger is called and the user can debug the program if just-in-time (JIT) debugging is enabled. If the user clicks **Ignore**, `assert` continues with normal execution. Note that clicking **Ignore** when an error condition exists can result in undefined behavior.

Since `assert` calls [`abort`](abort.md) immediately after displaying the message, the debug behavior for [`abort`](abort.md) will also occur. [`abort`](abort.md) will display a dialog box with the Abort, Retry, and Ignore buttons. This is not the same as the `assert` dialog box described above. In particular, [`abort`](abort.md) always exits the program during its execution, so neither the Retry nor Ignore button will resume execution following the `assert` call. The [`abort`](abort.md) dialog box is skipped if a dialog box was already displayed during `assert`, so this is only seen when output-to-stderr `assert` behavior is used.