+
+</PRE><H3><a name="h3-ERR_OK">ERR, OK</a></H3><PRE>
+ <EM>curses</EM> and <EM>terminfo</EM> routines frequently return these constant integral
+ values indicating failure and success, respectively.
+
+
+</PRE><H2><a name="h2-PREDEFINED-TYPES">PREDEFINED TYPES</a></H2><PRE>
+
+</PRE><H3><a name="h3-bool"><EM>bool</EM></a></H3><PRE>
+ X/Open Issue 4 <EM>curses</EM> (1996) preceded the ISO C99 and ISO C++98
+ standards, each of which also defined a Boolean data type. The <EM>curses</EM>
+ library requires an integral type <EM>bool</EM>.
+
+ <STRONG>ncurses</STRONG>' configure script attempts to discover the data type used by
+ the system's C and C++ compilers, to reuse for the <EM>curses</EM> <EM>bool</EM>.
+
+
+</PRE><H3><a name="h3-chtype"><EM>chtype</EM></a></H3><PRE>
+ The <EM>chtype</EM> integral type combines a ("narrow", 8-bit) character with
+ attributes encoding the character's <EM>rendition</EM>, such as the styling of
+ its typeface and/or foreground and background colors. See, for
+ example, <STRONG><A HREF="curs_addch.3x.html">addch(3x)</A></STRONG>, <STRONG><A HREF="curs_attr.3x.html">attron(3x)</A></STRONG>, and <STRONG><A HREF="curs_inch.3x.html">inch(3x)</A></STRONG>.
+
+
+</PRE><H3><a name="h3-cchar_t_attr_t"><EM>cchar_t,</EM> attr_t</a></H3><PRE>
+ <EM>chtype</EM> is too small for the standard C library's wide-character type,
+ <EM>wchar</EM><STRONG>_</STRONG><EM>t</EM>. <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM> is a type that can accommodate an <EM>attr</EM><STRONG>_</STRONG><EM>t</EM> and enough
+ wide characters to store what Unicode terms a <EM>grapheme</EM> <EM>cluster</EM> (a
+ "user-perceived character" [UAX #29], which may nevertheless require
+ several character encoding units to represent). <EM>attr</EM><STRONG>_</STRONG><EM>t</EM> is an integral
+ type storing "wide" attributes that apply to <EM>cchar</EM><STRONG>_</STRONG><EM>t</EM>s. See, for
+ example, <STRONG><A HREF="curs_add_wch.3x.html">add_wch(3x)</A></STRONG>, <STRONG><A HREF="curs_attr.3x.html">attr_on(3x)</A></STRONG>, and <STRONG><A HREF="curs_in_wch.3x.html">in_wch(3x)</A></STRONG>.
+
+
+</PRE><H3><a name="h3-SCREEN"><EM>SCREEN</EM></a></H3><PRE>
+ <EM>curses</EM> manages a terminal device with this structure type; see
+ <STRONG><A HREF="curs_initscr.3x.html">initscr(3x)</A></STRONG>.
+
+
+</PRE><H3><a name="h3-WINDOW"><EM>WINDOW</EM></a></H3><PRE>
+ <EM>curses</EM> represents rectangular portions of the terminal screen with the
+ <EM>WINDOW</EM> structure type; see subsection "Overview" of <STRONG><A HREF="ncurses.3x.html">ncurses(3x)</A></STRONG>.
+
+
+</PRE><H2><a name="h2-VARIABLES">VARIABLES</a></H2><PRE>
+
+</PRE><H3><a name="h3-curscr_stdscr_newscr">curscr, stdscr, newscr</a></H3><PRE>
+ The library records updates to the terminal screen in a window named
+ <STRONG>curscr</STRONG>. This object is referred to as the "physical screen" in
+ <STRONG><A HREF="curs_refresh.3x.html">curs_refresh(3x)</A></STRONG> and <STRONG><A HREF="curs_outopts.3x.html">curs_outopts(3x)</A></STRONG>.
+
+ <EM>ncurses</EM> collects pending updates to the terminal screen in a window
+ named <STRONG>newscr</STRONG>. This object is referred to as the "virtual screen" in
+ the <STRONG><A HREF="curs_kernel.3x.html">curs_kernel(3x)</A></STRONG>, <STRONG><A HREF="curs_refresh.3x.html">curs_refresh(3x)</A></STRONG>, and <STRONG><A HREF="curs_outopts.3x.html">curs_outopts(3x)</A></STRONG>. When the
+ screen is refreshed, <EM>curses</EM> determines a minimal set of updates using
+ the terminal's capabilities to make <STRONG>curscr</STRONG> look like <STRONG>newscr</STRONG>.
+
+ Once <EM>curses</EM> is initialized, it creates a window named <STRONG>stdscr</STRONG>. It is
+ the same size as the terminal screen and is the default window used by
+ routines that do not take a parameter identifying one. Many <EM>curses</EM>
+ functions use this window.
+
+
+</PRE><H3><a name="h3-COLORS">COLORS</a></H3><PRE>
+ Once <EM>curses</EM> is initialized, <STRONG>COLORS</STRONG> contains the number of colors
+ supported by the terminal; see <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>.
+
+
+</PRE><H3><a name="h3-COLOR_PAIRS">COLOR_PAIRS</a></H3><PRE>
+ Once <EM>curses</EM> is initialized, <STRONG>COLOR_PAIRS</STRONG> contains the number of color
+ pairs supported by the terminal; see <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>.
+
+
+</PRE><H3><a name="h3-COLS_LINES">COLS, LINES</a></H3><PRE>
+ Once <EM>curses</EM> is initialized, <STRONG>COLS</STRONG> and <STRONG>LINES</STRONG> contain the screen's width
+ and height in character cells, respectively; that is, the number of
+ columns and lines.
+
+
+</PRE><H3><a name="h3-ESCDELAY">ESCDELAY</a></H3><PRE>
+ For <EM>curses</EM> to distinguish the ESC character resulting from a user's
+ press of the "Escape" key on the input device from one beginning an
+ <EM>escape</EM> <EM>sequence</EM> (as commonly produced by function keys), it waits after
+ the escape character to see if further characters are available on the
+ input stream within a short interval. <STRONG>ESCDELAY</STRONG> stores this interval in
+ milliseconds.
+
+ If <STRONG><A HREF="curs_inopts.3x.html">keypad(3x)</A></STRONG> is disabled for the <EM>curses</EM> window receiving input, a
+ program must disambiguate escape sequences itself.
+
+
+</PRE><H3><a name="h3-TABSIZE">TABSIZE</a></H3><PRE>
+ The <EM>curses</EM> library converts a tab character to this number of spaces as
+ it adds a tab to a window; see <STRONG><A HREF="curs_addch.3x.html">curs_addch(3x)</A></STRONG>.
+
+
+</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
+ Either <STRONG><A HREF="curs_initscr.3x.html">initscr(3x)</A></STRONG> or <STRONG><A HREF="curs_initscr.3x.html">newterm(3x)</A></STRONG> initializes <EM>curses</EM>.
+
+ If <EM>ncurses</EM> is configured to provide separate <EM>curses</EM> and <EM>tinfo</EM>
+ libraries, most of these variables reside in the former.
+
+
+</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
+ The X/Open Curses standard documents all of the foregoing types and
+ symbols except for <STRONG>newscr</STRONG>, <STRONG>TABSIZE</STRONG>, and <STRONG>ESCDELAY</STRONG>.
+
+ X/Open Curses describes <STRONG>curscr</STRONG> only as "an internal data structure";
+ SVr4 gave more details, noting its use "for certain low-level
+ operations like clearing and redrawing a screen containing garbage".
+ Neither specified its interaction with the rest of the interface beyond
+ use as an argument to <STRONG><A HREF="curs_outopts.3x.html">clearok(3x)</A></STRONG> and <STRONG><A HREF="curs_refresh.3x.html">wrefresh(3x)</A></STRONG>.
+
+ <STRONG>newscr</STRONG> is a feature of SVr4 <EM>curses</EM>. When refreshing the screen, it is
+ used as a working area for combining the standard window <STRONG>stdscr</STRONG> with
+ any others the application may have created with <STRONG><A HREF="curs_window.3x.html">newwin(3x)</A></STRONG>. When the
+ update of <STRONG>newscr</STRONG> is complete, <EM>curses</EM> modifies <STRONG>curscr</STRONG> to match <STRONG>newscr</STRONG>.
+
+ <STRONG>TABSIZE</STRONG> is a feature of SVr4 <EM>curses</EM>.
+
+ <STRONG>o</STRONG> SVr4 initially sets <STRONG>TABSIZE</STRONG> from the terminal description's
+ <STRONG>init_tabs</STRONG> capability. After that, it can be altered by
+ applications using SVr4 <EM>curses</EM>.
+
+ <STRONG>o</STRONG> SVr4 <EM>curses</EM> uses the value of <STRONG>TABSIZE</STRONG> to compute the position of
+ tab stops when updating both the virtual screen with <STRONG><A HREF="curs_addch.3x.html">addch(3x)</A></STRONG> and
+ the physical screen with <STRONG><A HREF="curs_terminfo.3x.html">mvcur(3x)</A></STRONG>.
+
+ <STRONG>o</STRONG> <EM>ncurses</EM> uses the value of <STRONG>TABSIZE</STRONG> only to update the virtual
+ screen. It uses the terminal description's "<STRONG>it</STRONG>" (<STRONG>init_tabs</STRONG>)
+ capability for computing hardware tabs (that is, tab stops on the
+ physical screen).
+
+ <STRONG>o</STRONG> Other implementations differ. For instance, NetBSD <EM>curses</EM> allows
+ <STRONG>TABSIZE</STRONG> to be set through an environment variable. <EM>ncurses</EM> does
+ not.
+
+ NetBSD <EM>curses</EM> does not support hardware tabs; it uses the <STRONG>init_tabs</STRONG>
+ capability and the <STRONG>TABSIZE</STRONG> variable only for updating the virtual
+ screen.
+
+ <STRONG>ESCDELAY</STRONG> is a feature of AIX <EM>curses</EM>.
+
+ <STRONG>o</STRONG> In AIX, the units for <STRONG>ESCDELAY</STRONG> are <EM>fifths</EM> of milliseconds.
+
+ <STRONG>o</STRONG> The default value for AIX's <STRONG>ESCDELAY</STRONG> equals 0.1 seconds.
+
+ <STRONG>o</STRONG> AIX also enforces a limit of 10,000 seconds for <STRONG>ESCDELAY</STRONG>; <EM>ncurses</EM>
+ does not enforce any upper limit.
+
+ <EM>ncurses</EM> has long used <STRONG>ESCDELAY</STRONG> with units of milliseconds, making it
+ impossible to be completely compatible with AIX. Consequently, most
+ users have decided either to override the value, or to rely upon its
+ default.
+
+
+</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
+ <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>, <STRONG><A HREF="curs_opaque.3x.html">curs_opaque(3x)</A></STRONG>, <STRONG><A HREF="curs_terminfo.3x.html">curs_terminfo(3x)</A></STRONG>,
+ <STRONG><A HREF="curs_threads.3x.html">curs_threads(3x)</A></STRONG>, <STRONG><A HREF="term_variables.3x.html">term_variables(3x)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>
+
+ [UAX #29] "Unicode Standard Annex #29: Unicode Text Segmentation";
+ <https://unicode.org/reports/tr29/>