-No error conditions are defined.
-If the \fIchstr\fP parameter is null,
-no data is returned,
-and the return value is zero.
+X/Open Curses defines no error conditions.
+In this implementation:
+.bP
+If the \fIwin\fP parameter is null, an error is returned,
+.bP
+If the \fIchstr\fP parameter is null, an error is returned,