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.\" $Id: curs_color.3x,v 1.188 2026/09/19 20:59:23 tom Exp $
.TH curs_color 3X 2026-09-19 "ncurses 6.6" "Library calls"
.ie \n(.g \{\
.ds `` \(lq
.ds '' \(rq
.\}
.el \{\
.ie t .ds `` ``
.el   .ds `` ""
.ie t .ds '' ''
.el   .ds '' ""
.\}
.
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.
.SH NAME
\fB\%start_color\fP,
\fB\%has_colors\fP,
\fB\%can_change_color\fP,
\fB\%init_pair\fP,
\fB\%init_color\fP,
\fB\%init_extended_pair\fP,
\fB\%init_extended_color\fP,
\fB\%color_content\fP,
\fB\%pair_content\fP,
\fB\%extended_color_content\fP,
\fB\%extended_pair_content\fP,
\fB\%reset_color_pairs\fP,
\fB\%COLOR_PAIR\fP,
\fB\%PAIR_NUMBER\fP,
\fB\%COLORS\fP,
\fB\%COLOR_PAIRS\fP,
\fB\%COLOR_BLACK\fP,
\fB\%COLOR_RED\fP,
\fB\%COLOR_GREEN\fP,
\fB\%COLOR_YELLOW\fP,
\fB\%COLOR_BLUE\fP,
\fB\%COLOR_MAGENTA\fP,
\fB\%COLOR_CYAN\fP,
\fB\%COLOR_WHITE\fP,
\fB\%A_COLOR\fP \-
manipulate terminal colors with \fIcurses\fR
.SH SYNOPSIS
.nf
\fB#include <curses.h>
.PP
\fI/* variables */
\fBint COLOR_PAIRS;
\fBint COLORS;
.PP
\fBint start_color(void);
.PP
\fBbool has_colors(void);
\fBbool can_change_color(void);
.PP
\fBint init_pair(short \fIpair\fP, short \fIf\fP, short \fIb\fP);
\fBint init_color(short \fIindex\fP, short \fIr\fP, short \fIg\fP, short \fIb\fP);
\fI/* extensions */
\fBint init_extended_pair(int \fIpair\fP, int \fIf\fP, int \fIb\fP);
\fBint init_extended_color(int \fIindex\fP, int \fIr\fP, int \fIg\fP, int \fIb\fP);
.PP
\fBint color_content(short \fIindex\fP, short *\fIr\fP, short *\fIg\fP, short *\fIb\fP);
\fBint pair_content(short \fIpair\fP, short *\fIf\fP, short *\fIb\fP);
\fI/* extensions */
\fBint extended_color_content(int \fIindex\fP, int *\fIr\fP, int *\fIg\fP, int *\fIb\fP);
\fBint extended_pair_content(int \fIpair\fP, int *\fIf\fP, int *\fIb\fP);
.PP
\fI/* extension */
\fBvoid reset_color_pairs(void);
.PP
\fI/* macros */
\fBint COLOR_PAIR(int \fIn\fP);
\fBPAIR_NUMBER(int \fIattr\fP);
\fBCOLOR_BLACK
\fBCOLOR_RED
\fBCOLOR_GREEN
\fBCOLOR_YELLOW
\fBCOLOR_BLUE
\fBCOLOR_MAGENTA
\fBCOLOR_CYAN
\fBCOLOR_WHITE
\fBA_COLOR
.fi
.SH DESCRIPTION
.I curses
supports color rendering on terminals with applicable capabilities.
Once the library has initialized the terminal,
.B \%has_colors
tells an application whether that terminal type has color capability.
If it does,
calling
.B \%start_color
enables the feature.
(See section \*(``NOTES\*('' below regarding \fB\%ripoffline\fP(3X).)
.PP
When applying colors to a
.I curses
window,
the library manages them in pairs.
A
.I "color pair"
couples a foreground color applied
to the visible strokes of a glyph
with a background color for the field in the character cell
within which the glyph appears.
Configure at least one color pair to use the color feature.
.B \%init_pair
initializes a color pair identifier,
whose value you select,
from a pair of
.I "color indices,"
foreground and background.
Each index represents a color.
X/Open Curses standardizes,
and a
.I curses
library defines,
a small set of color indices;
see section \*(``MACROS\*('' below.
The macro
.B \%COLOR_PAIR(\fIn\fP)
converts a pair
.I n
thus initialized to the value required to encode it in a
.I \%chtype
or
.IR \%attr_t "."
Another macro,
.B \%PAIR_NUMBER(\fIn\fP)
conversely extracts a color pair identifier
from variables of those data types.
.B \%pair_content
permits discovery of a color pair's current definition.
.B \%color_content
extracts the
red,
green,
and blue components of the color using the given index.
.PP
.B \%can_change_color
tells an application whether the terminal type
permits (re)definition of a color.
If it does,
you can call
.B \%init_color
to update the specified color index to use
red,
green,
and blue components of your choice.
.PP
Subsection \*(``Color Handling\*('' of \fB\%terminfo\fP(5)
describes the capabilities that terminal types use to manage color.
.PP
Passing a
.I curses
function
a color index outside the range
.B 0
to
.BR \%COLORS\-1 ","
or a color pair identifier outside the range
.B 0
to
.B \%COLOR_PAIRS\-1
may result in a runtime error.
.B COLORS
corresponds to the terminal type's
.B \%max_colors
.RB \%( colors )
capability,
and
.B \%COLOR_PAIRS
to
.B \%max_pairs
.RB \%( pairs ).
.I \%ncurses
permits specification of a color index of
.B \-1
in certain extended functions to select a
.IR "default color" ";"
see \fB\%use_default_colors\fP(3X).
.PP
Color pair
.B 0
is special;
it denotes \*(``no color\*('',
meaning the terminal's
(typically monochrome)
power-up default fore- and background.
.PP
For each screen,
.I \%ncurses
maintains a
.I "color palette"
that maps color indices into the RGB
(red,
green,
blue)
color space.
.SH VARIABLES
.SS COLORS
is initialized by \fB\%start_color\fP to the maximum number of colors
the terminal can support.
.SS COLOR_PAIRS
is initialized by \fB\%start_color\fP to the maximum number of color
pairs the terminal can support.
Often,
its value is the product \fB\%COLORS\fP \(mu \fB\%COLORS\fP,
but this is not always true.
.bP
A few terminals use the HLS color space,
ignoring this rule;
and
.bP
while a terminal type may support many colors,
a portable
.I curses
application is limited
to the number of distinct color indices and color pair identifiers
that a
.I "signed short"
value can represent.
.SH FUNCTIONS
.SS has_colors
.B \%has_colors
returns
.B TRUE
if the terminal supports colors and
.B FALSE
if it does not.
\fB\%initscr\fP(3X) or \fB\%newterm\fP(3X) must be called first,
but
.B \%start_color
need not be.
An application might call
.B \%has_colors
to inform its decision whether to use color
or a video attribute like
.B \%A_BOLD
to render text.
.SS start_color
If your application requires color,
call
.B \%start_color
before any other color manipulation function.
As a rule,
do so immediately after
.BR \%initscr "."
If the terminal type supports color,
.BR \%start_color ":"
.bP
initializes the two global variables,
.B \%COLORS
and
.BR \%COLOR_PAIRS ","
described above;
.bP
initializes (only) the color pair
.B 0
to the terminal type's power-up foreground and background colors
(but see the
.I \%ncurses
extension \fB\%use_default_colors\fP(3X));
.bP
initializes the color palette;
and
.bP
selects color pair
.BR 0 "."
.\" ...by calling internal functions `set_{fore,back}ground_color()`.
.PP
.B \%start_color
sets up the color palette
for the eight colors named by the X/Open Curses standard
(see section \*(``CONSTANTS\*('' above)
applying weights appropriate to the color space.
.I curses
does not attempt to initialize the color palette
to match a terminal type's power-up configuration.
.\" Init and reset string capabilities could do so.
See section \*(``NOTES\*('' below.
.PP
Calling
.B \%start_color
again after it has returned
.B OK
does nothing.
.SS init_pair
(Re-)define a color pair with
.BR \%init_pair ","
which takes three arguments:
the color pair identifier to be updated,
a foreground color index,
and
a background color index.
A portable application restricts these argument values
to the valid ranges stated above.
If the application uses
.IR \%ncurses 's
default color extension
(see below),
the library adjusts the upper limit to allow for extra pairs
that use a default color in the foreground and/or background.
.PP
If a color pair was previously defined,
.B \%init_pair
causes a refresh of the entire screen,
and all occurrences of that color pair change to use its new definition.
.I \%ncurses
suppresses this refresh if the color pair's new color indices
are the same as the old.
.PP
.I \%ncurses
extensions
allow you to update color pair
.B 0
via \fB\%assume_default_colors\fP(3X),
and to access the terminal's default colors as color index
.B \-1
if you first call \fB\%use_default_colors\fP(3X).
.SS init_extended_pair
Because
.B \%init_pair
uses signed
.IR short s
for its parameters,
its color pair identifiers and color indices
are limited to 32767 even for terminal types that are much more capable.
.\" ...not 65535 because the System V terminfo compiled entry format
.\" foreclosed use of an unsigned type for this purpose and others.
This
.I \%ncurses
extension uses
.IR int s
instead,
expanding their range.
.SS pair_content
An application can discover the color index assignments of a color pair
with
.BR \%pair_content "."
Its first argument is the color pair identifier of interest,
and the remaining two are each a pointer to
.I short
that the function populates
with the foreground and background color indices,
respectively.
.SS extended_pair_content
Because
.B \%pair_content
uses signed
.IR short s
for its parameters,
its color pair identifiers and color indices
are limited to 32767 even for terminal types that are much more capable.
.\" ...not 65535 because the System V terminfo compiled entry format
.\" foreclosed use of an unsigned type for this purpose and others.
This
.I \%ncurses
extension uses
.IR int s
instead,
expanding their range.
.SS reset_color_pairs
This
.I \%ncurses
extension directs the library to discard
all color pair assignments configured by application calls of
.B \%init_pair
and
.BR \%init_extended_pair "."
.\" Due to the library's internal design, this has the effect of
.\" resetting color pair zero, so it still exists and works afterward.
It furthermore marks the entire screen as requiring refresh;
an application can thus easily reconfigure its color scheme
by subsequently initializing as many color pairs as required.
.SS can_change_color
.B \%can_change_color
returns
.B TRUE
if the terminal supports colors and can change their mappings,
and
.B FALSE
if it does not.
.SS init_color
Change a color's mapping (definition) by supplying this function
four arguments:
the color index;
and
red,
green,
and
blue
color channel values in the range 0-1000.
.PP
If the color index is in use in a color pair on the screen,
all occurrences of it change to use its new definition.
No \fB\%refresh\fP(3X) is necessary.
.\" The library essentially does `putp(tiparm("initc", idx, r, g, b));`.
.\" But for the interposition of the higher-level color palette ncurses
.\" stores in `SCREEN`, `init_color` would be a "lower-level" API, like
.\" `mvcur()`.
.SS init_extended_color
Because
.B \%init_color
uses signed
.IR short s
for its parameters,
the maximum value of its color index argument
is limited to 32767 even for terminal types that are much more capable.
(The range of valid RGB channel values remains 0-1000.)
.\" Here the System V terminfo compiled entry format imposes no
.\" limitation, because these values exist only as parameters to string
.\" capabilities.  We still say "32767" because that is the smallest
.\" possible maximum value of a `signed short` in standard C.
This
.I \%ncurses
extension uses
.IR int s
instead,
expanding the range of permissible color indices.
.PP
If the color index is in use in a color pair on the screen,
all occurrences of it change to use its new definition.
No \fB\%refresh\fP(3X) is necessary.
.\" The library essentially does `putp(tiparm("initc", idx, r, g, b));`.
.\" But for the interposition of the higher-level color palette ncurses
.\" stores in `SCREEN`, `init_extended_color` would be a "lower-level"
.\" API, like `mvcur()`.
.SS color_content
An application can query a color index's location in RGB space
by calling
.BR \%color_content .
The library stores the color channel values
corresponding to the specified color index
in the
.IR red ","
.IR green ","
and
.I blue
.RI pointer-to- short
arguments.
.SS extended_color_content
Because
.B \%color_content
uses signed
.IR short s
for its parameters,
the maximum value of its color index argument
is limited to 32767 even for terminal types that are much more capable.
This
.I \%ncurses
extension uses
.IR int s
instead,
expanding the range of permissible color indices.
.SH MACROS
.\" We do _not_ mention ANSI X3.64 here.  It was initially issued in
.\" (or at least dated) 1979, and reputedly, was never revised or
.\" updated prior its withdrawal in 1994.  ANSI X3.64 did not address
.\" color features.
.\" See <https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub86.pdf>,
.\" p. H-1 (PDF p. 81).
ISO\ 6429 and ECMA-48
define eight standard colors
(known inaccurately as \*(``ANSI\*('' colors),
to which X/Open Curses assigns symbolic names as object-like macros
.BR \%COLOR_BLACK ","
.BR \%COLOR_RED ","
.BR \%COLOR_GREEN ","
.BR \%COLOR_YELLOW ","
.BR \%COLOR_BLUE ","
.BR \%COLOR_MAGENTA ","
.BR \%COLOR_CYAN ","
and
.BR \%COLOR_WHITE "."
.I curses
assumes that
.B \%COLOR_BLACK
is the default background color for all terminals.
.I \%ncurses
offers an extension to override that assumption;
see \fB\%assume_default_colors\fP(3X).
Some terminals support additional colors that lack standard names.
.PP
.B \%A_COLOR
is a bit mask that,
when bitwise \*(``and\*(''-ed with a
.IR \%chtype ","
extracts its color pair identifier.
X/Open Curses mandates the provision of two function-like macros.
They have no application in the wide-character API of
.IR curses "."
.SS COLOR_PAIR
.BI \%COLOR_PAIR( n )
replaces color pair identifier
.I n
with its encoded value appropriate for use in a
.IR chtype "."
Such values have a limited,
implementation-dependent range.
Non-wide API functions such as \fB\%attrset\fP(3X)
cannot handle larger color pair identifiers than this.
A portable application checks that
.IR n 's
value is less than
.I COLOR_PAIRS
before employing this macro on it.
If you need to transform a larger color pair identifier,
you must use the wide API and call,
for example,
\fB\%attr_set\fP(3X),
which passes the color pair identifier
as a parameter separate from the attributes.
.SS PAIR_NUMBER
.BI \%PAIR_NUMBER( n )
replaces its
.I chtype
or
.I attr_t
argument
.I n
with the color pair identifier encoded within it.
.\" X/Open Curses Issue 7 explains that terribly; see p. 57 (PDF p. 71).
.PP
.B \%COLOR_PAIR()
and
.B \%PAIR_NUMBER()
are inverse operations.
.SH RETURN VALUE
.B \%can_change_color
and
.B \%has_colors
return
.B TRUE
or
.BR FALSE "."
The other functions return
.B OK
on success and
.B ERR
on failure.
.PP
In
.IR \%ncurses ","
color manipulation functions returning an
.I int
recognize several error conditions.
.bP
All return
.B ERR
if the screen has not been initialized;
see \fBinitscr\fP(3X) or \fBnewterm\fP(3X).
.bP
All except
.B \%start_color
return
.B ERR
if
.B \%start_color
has not been called,
or itself returned
.BR ERR "."
.bP
.B \%start_color
returns
.B ERR
if it cannot allocate memory for its color pair table.
.bP
.B \%init_color
returns
.B ERR
if the terminal type does not support assignable color values;
that is,
if the
.B \%initialize_color
.RB ( initc )
capability is absent from its description.
.bP
.B \%init_color
returns
.B ERR
if any of its
.IR r ","
.IR g ","
.I b
arguments is outside the range 0-1000 inclusive.
.bP
.BR \%init_pair ","
.BR \%init_color ","
.BR \%init_extended_pair ","
.BR \%init_extended_color ","
.BR \%color_content ","
.BR \%pair_content ","
.BR \%extended_color_content ","
and
.B \%extended_pair_content
return
.B ERR
on attempts to use
.RS
.bP
color identifiers outside the range
.RB \%0- COLORS \-1
inclusive,
the default colors extension notwithstanding,
or
.bP
color pair identifiers outside the range
.RB \%0- COLOR_PAIRS \-1
inclusive.
.RE
.SH NOTES
X/Open Curses says nothing about how the standard colors
are to be configured in a color space.
.I \%ncurses
initializes a screen's color palette such that,
in the RGB color space,
each channel of the eight standard colors has a value of either
.B 680
or
.BR 0 "."
If the terminal type supports at least 16 colors,
this configuration aids an application
to support a terminal type with only one typeface
to simulate bold text with \*(``bright\*('' colors.
With appropriate configuration of the bright color pairs
by the application,
increasing nonzero channel values to
.BR 1000 ","
this scheme suffices to approximate the 16 colors
.\" ...that we can think of as a 4-bit RGBI color space...
of IBM CGA text mode video
and the power-up configuration of the DEC VT525.
.\" XXX: What does the following mean?  ncurses does not initialize
.\" palette entries for colors beyond the standard 8.  See the
.\" `cga_palette` struct in ncurses/base/lib_color.c.  Who wrote this?
.\" --GBR
.\"After the initial eight colors
.\"(if the terminal supports more than eight colors)
.\"the components are initialized using the same pattern,
.\"but with weights of \fB1000\fP.
SVr4
.I curses
instead assigns values of
.B 1000
to the nonzero color channel values of the eight standard colors.
.PP
Setting a background color via a color pair identifier
affects only character cells
that a character write operation explicitly touches.
To change the background color used
when parts of a window are blanked by erasing or scrolling operations,
see \fB\%bkgd\fP(3X)
(wide-character API users: \fB\%bkgrnd\fP(3X)).
.PP
Windows created by \fB\%ripoffline\fP(3X)
do not inherit color pair configuration applied to
.IR stdscr ";"
they must be configured independently.
.PP
In
.IR \%ncurses ","
.B \%init_pair
accepts negative foreground and background color arguments
to support its \fB\%use_default_colors\fP(3X) extension,
but only after the latter function has been called.
.PP
The assumption that
.B \%COLOR_BLACK
is the terminal's default background color can be overridden using
.IR \%ncurses 's
\fB\%assume_default_colors\fP(3X) extension.
.PP
In
.IR \%ncurses ","
each pointer passed to
.B \%color_content
and
.B \%pair_content
can be null,
in which case the library ignores it,
permitting the application to disregard unnecessary information.
.PP
In
.IR \%ncurses ","
each screen has a
color activation flag,
color palette,
color pair table,
and associated
.B \%COLORS
and
.B \%COLOR_PAIRS
values;
.B \%start_color
affects only the current screen.
The SVr4
.I curses
interface,
standardized by X/Open Curses,
was not designed with distinguishable screens clearly in mind;
historical implementations may use a single shared color palette
for all screens the library manages.
.PP
Several caveats apply to emulation of the CGA/EGA/VGA video
of IBM PC-compatible machines of the 80486 era and earlier.
.bP
.B \%COLOR_YELLOW
was frequently converted,
in the analog domain,
to a shade of brown if the intensity bit was not set.
.\" https://nerdlypleasures.blogspot.com/2023/03/the-saga-of-color-brown-in-early-years.html
To get yellow on such devices,
one would combine
.B \%COLOR_YELLOW
with the
.B \%A_BOLD
attribute.
.bP
The
.B \%A_BLINK
attribute should in theory make the background bright.
This often fails to work,
and even VGA controllers for which it mostly works,
such as those from Paradise and compatibles,
do the wrong thing
when you try to set a bright \*(``yellow\*('' background \(em
you get a blinking yellow foreground instead.
.bP
Color RGB values are not configurable on these devices
(in text mode).
.SS "Why This Color Model?"
A programmer new to
.I curses
may wonder why the library works with pairs of indexed colors
instead of \*(``direct\*('' foreground and background RGB triples.
The answer lies in the limited bandwidth between terminals
and their time-sharing host machines.
In the 1980s,
a 9600bps serial link was considered fast.
That speed typically corresponded to a data rate
of 960 bytes per second.
.\" Consider BSD curses's single "standout" attribute occupying the most
.\" significant bit of a 7-bit ASCII-encoded character cell, and 8N1
.\" transmission.  (There is always 1 start bit, thus 8N1 -> 10 bits.)
Using a single-byte character encoding,
refreshing an 80\(mu24 terminal screen took two full seconds.
In other words,
such a terminal refreshing its entire screen contents
rendered half a frame per second.
Adding data to each character cell
necessary for the \*(``direct\*('' color model
at 8 bits per color channel
would add 6 bytes to every character cell,
extending the full-screen refresh time to 14 seconds.
Even a pair of 8-bit color values would triple the refresh time.
.PP
Moreover,
the vast majority of
.I curses
applications do not demand a wide gamut of colors.
Even a colorful application like the game \fB\%nethack\fP(6)
renders most of its interface in monochrome by default.
A text user interface
employing the \fBform\fP(3X) or \fBmenu\fP(3X) libraries
often uses fewer than ten distinct colors at any one time.
Thus,
small integers suffice both to index individual colors
and to pair them.
Typically,
each color pair is assigned to a type of user interface element,
like a button or scroll bar control.
Further,
in the original SVr3.2
.I curses
implementation of color and today still in
.IR ncurses 's
non-wide library,
.I chtype
affords few bits for encoding of the color pair identifier.
.PP
Even in the common modern scenario where a terminal emulator
runs on the same host as the
.I curses
application,
and available bandwidth is limited only by the speed of the system bus,
efficient encoding of character cell data aids performance
by minimizing the copies to and from the kernel's memory space
by use of the pseudoterminal (pty) system interface.
For example,
in the Linux 7.2 kernel,
the pty buffer size is 4\ KiB,
ensuring a CPU mode switch every time it fills up.
.\" https://www.kernel.org/doc/html/v7.2/driver-api/tty/n_tty.html
Parsimonious data management also reduces memory cache pressure.
.SH EXTENSIONS
The functions marked as extensions originated in
.IR \%ncurses ","
and are not found in SVr4
.IR curses ,
4.4BSD
.IR curses ,
or any other previous
.I curses
implementation.
.SH PORTABILITY
Applications employing
.I \%ncurses
extensions should condition their use on the visibility of the
.B \%NCURSES_VERSION
preprocessor macro.
.PP
X/Open Curses Issue\ 4 describes these functions.
It specifies no error conditions for them.
.PP
.I \%ncurses
satisfies X/Open Curses's minimum maximums for
.I \%COLORS
and
.IR \%COLOR_PAIRS "."
.PP
.I \%ncurses
does not refresh the screen if
.B \%init_pair
is used to no effect on an existing color pair.
.PP
X/Open Curses does not specify a limit for the number of color indices
and color pair identifiers a terminal can support.
However,
in its use of
.I short
for the parameters,
it carries over SVr4's implementation detail for the compiled
.I \%term\%info
database,
which uses signed 16-bit numbers.
.I \%ncurses
provides extended versions of the functions using
.I int
parameters,
allowing applications to use larger index and pair identifiers.
.PP
SVr4
.I curses
returns
.I ERR
from
.I \%pair_content
if its
.I pair
argument
was not initialized using
.IR \%init_pairs ,
and from
.I \%color_content
if the terminal does not support changing colors.
.I \%ncurses
does neither.
.SH HISTORY
SVr3.2 (1988) introduced color support to
.I curses
with all of the symbols
in the synopsis above except those marked as extensions.
It reserved color pair 0 as the terminal's initial,
\*(``uncolored\*('' state,
.\" "we assume that color 0 is always a default background.", SVr3.2
.\" usr/src/lib/libcurses/screen/start_col.c
and limited the number of possible color pairs to 64,
because the color pair datum was encoded in six bits of a
.IR \%chtype "."
.PP
SVr4 (1989) made only internal changes,
such as moving the storage of color state
from the
.I SCREEN
structure
(pointed to by
.IR SP )
to the
.I \%TERMINAL
structure
(pointed to by
.IR \%cur_term ")."
.PP
Other
.I curses
implementations impose different limits
on the number of color indices and color pairs.
.bP
.I \%PCCurses
(1987-1990) provided for only 8 color indices
(and therefore permitted at most 8\(mu8 = 64 color pairs).
.bP
.I \%PDCurses
(1992-present) initially inherited the 8-color limitation from
.IR \%PCCurses ","
but increased it to 256 in version 2.5 (2001),
and widened its
.I \%chtype
from 16 to 32 bits.
.bP
X/Open Curses (1992-present)
specified a new integral type,
.IR attr_t ","
storing rendering attributes
(see \fB\%attr_on\fP(3X))
and a color pair identifier,
and a new structure type,
.IR \%cchar_t ","
to store a sequence of wide character codes
separately from the character cell's attributes and color pair,
allowing an increased range of color pairs.
The standard specifies
.I attr_t
as a
.IR short ","
limiting portable values to 15 bits;
negative values are invalid in System\ V.
.bP
.I \%ncurses
(1992-present),
in its non-wide-character configuration,
uses 8 bits of
.I \%chtype
for the color pair identifier.
.IP
Version 5.3 (2002) introduced a wide-character interface,
but encoded the color pair identifier with attributes
in the character type.
.IP
Since version 6 (2015),
.I \%ncurses
uses a separate
.I int
for the color pair identifier in a
.IR \%cchar_t ","
adding extension functions to manage the wider type.
When a color pair identifier fits in 8 bits,
.I \%ncurses
permits manipulation of color pair identifiers with functions taking
.I \%chtype
arguments,
even when a
.I curses
window uses wide-character cells.
.bP
NetBSD
.I curses
used 6 bits for the color pair identifier from 2000
(when it first added color support)
until 2004.
At that point,
NetBSD widened the color pair identifier to use 9 bits.
As of 2025,
that size is unchanged.
.\" http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libcurses/curses.h?rev=1.133
.\" indicates a mask of 0x03fe0000.
Like
.I \%ncurses
before version 6,
the NetBSD color pair identifier is stored in
the attributes field of
.IR \%cchar_t ","
limiting the number of color pairs.
.PP
.I \%ncurses
6.1 (2018) introduced
.IR \%init_extended_pair ","
.IR \%init_extended_color ","
.IR \%extended_pair_content ","
.IR \%extended_color_content ","
and
.IR \%reset_color_pairs "."
.SH SEE ALSO
\fB\%curses\fP(3X),
\fB\%curs_attr\fP(3X),
\fB\%curs_initscr\fP(3X),
\fB\%curs_variables\fP(3X),
\fB\%default_colors\fP(3X)