-X/Open defines no error conditions.
-In this implementation,
-if the window parameter is null or the str parameter is null,
-a zero is returned.
+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,