+ X/Open defines no error conditions. In this implementa-
+ tion
+
+ <STRONG>delwin</STRONG>
+ returns an error if the window pointer is null, or if
+ the window is the parent of another window.
+
+ <STRONG>derwin</STRONG>
+ returns an error if the parent window pointer is
+ null, or if any of its ordinates or dimensions is
+ negative, or if the resulting window does not fit in-
+ side the parent window.
+
+ <STRONG>dupwin</STRONG>
+ returns an error if the window pointer is null.
+
+ This implementation also maintains a list of windows,
+ and checks that the pointer passed to <STRONG>delwin</STRONG> is one
+ that it created, returning an error if it was not..
+
+ <STRONG>mvderwin</STRONG>
+ returns an error if the window pointer is null, or if
+ some part of the window would be placed off-screen.
+
+ <STRONG>mvwin</STRONG>
+ returns an error if the window pointer is null, or if
+ the window is really a pad, or if some part of the
+ window would be placed off-screen.
+
+ <STRONG>newwin</STRONG>
+ will fail if either of its beginning ordinates is
+ negative, or if either the number of lines or columns
+ is negative.
+
+ <STRONG>syncok</STRONG>
+ returns an error if the window pointer is null.
+
+ <STRONG>subwin</STRONG>
+ returns an error if the parent window pointer is
+ null, or if any of its ordinates or dimensions is
+ negative, or if the resulting window does not fit in-
+ side the parent window.
+
+ The functions which return a window pointer may also fail
+ if there is insufficient memory for its data structures.
+ Any of these functions will fail if the screen has not
+ been initialized, i.e., with <STRONG>initscr</STRONG> or <STRONG>newterm</STRONG>.
+