This variable has meaning only on graphical systems such as Windows. Use WIN_ERROR_HANDLING to control how hardware errors are handled.
When this variable is set to the default of 1 (on, true, yes), certain errors are handled directly by the host environment, and do not automatically return a file error code. For these errors, a dialog box is displayed that describes the error and offers Cancel and Retry buttons. The user may correct the error and press Retry. If the user presses Cancel, then your program receives the file error that it would have normally received.
If you set WIN_ERROR_HANDLING to 0 (off, false, no), then the dialog box is not shown, and your program receives the error directly.