-</PRE><H3><a name="h3-Unset-TERM-Variable">Unset TERM Variable</a></H3><PRE>
- If the TERM variable is missing or empty, <STRONG>initscr</STRONG> uses the value "un-
- known", which normally corresponds to a terminal entry with the <EM>generic</EM>
- (<EM>gn</EM>) capability. Generic entries are detected by <STRONG>setupterm</STRONG> (see
- <STRONG><A HREF="curs_terminfo.3x.html">curs_terminfo(3x)</A></STRONG>) and cannot be used for full-screen operation. Other
- implementations may handle a missing/empty TERM variable differently.
+ <STRONG>o</STRONG> Since version 4.0 (1996), <EM>ncurses</EM> has maintained a list of all
+ windows for each screen, using that information to delete those
+ windows when <STRONG>delscreen</STRONG> is called.
+
+ <STRONG>o</STRONG> NetBSD copied this feature of <EM>ncurses</EM> in 2001. PDCurses follows
+ the SVr4 model, deleting only the standard <EM>WINDOW</EM> structures.
+
+
+</PRE><H3><a name="h3-High-level-versus-Low-level">High-level versus Low-level</a></H3><PRE>
+ Different implementations may disagree regarding the level of some
+ functions. For example, <EM>SCREEN</EM> (returned by <STRONG>newterm</STRONG>) and <EM>TERMINAL</EM>
+ (returned by <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG>) hold file descriptors for the output
+ stream. If an application switches screens using <STRONG>set_term</STRONG>, or switches
+ terminals using <STRONG><A HREF="curs_terminfo.3x.html">set_curterm(3x)</A></STRONG>, applications which use the output file
+ descriptor can have different behavior depending on which structure
+ holds the corresponding descriptor.
+
+ For example
+
+ <STRONG>o</STRONG> NetBSD's <STRONG><A HREF="curs_termattrs.3x.html">baudrate(3x)</A></STRONG> function uses the descriptor in <EM>TERMINAL</EM>.
+ <EM>ncurses</EM> and SVr4 use the descriptor in <EM>SCREEN</EM>.
+
+ <STRONG>o</STRONG> NetBSD and <EM>ncurses</EM> use the descriptor in <EM>TERMINAL</EM> for terminal I/O
+ modes, e.g., <STRONG><A HREF="curs_kernel.3x.html">def_shell_mode(3x)</A></STRONG>, <STRONG><A HREF="curs_kernel.3x.html">def_prog_mode(3x)</A></STRONG>. SVr4 curses
+ uses the descriptor in <EM>SCREEN</EM>.
+
+ <STRONG>Unset</STRONG> <EM>TERM</EM> <STRONG>Variable</STRONG>
+ If the <EM>TERM</EM> variable is missing or empty, <STRONG>initscr</STRONG> uses the value
+ "unknown", which normally corresponds to a terminal entry with the
+ <EM>generic</EM> (<EM>gn</EM>) capability. Generic entries are detected by <STRONG><A HREF="curs_terminfo.3x.html">setupterm(3x)</A></STRONG>
+ and cannot be used for full-screen operation. Other implementations
+ may handle a missing/empty <EM>TERM</EM> variable differently.