+Goodheart did not mention the background character or the \fBcchar_t\fP type.
+Those are respectively SVr4 and X/Open features.
+He did mention the \fBA_\fP constants, but did not indicate their values.
+Those were not the same in different systems,
+even for those marked as System V.
+.PP
+Different Unix systems used different sizes for the bit-fields in \fBchtype\fP
+for \fIcharacters\fP and \fIcolors\fP, and took into account the different
+integer sizes (32-bit versus 64-bit).
+.PP
+This table showing the number of bits for \fBA_COLOR\fP
+and \fBA_CHARTEXT\fP
+was gleaned from the curses header files for
+various operating systems and architectures.
+The inferred architecture and notes reflect
+the format and size of the defined constants
+as well as clues such as the alternate character set implementation.
+A 32-bit library can be used on a 64-bit system,
+but not necessarily the reverse.
+.PP
+.TS
+Lb Lb Lb Cb S Lb
+Lb2 Lb Lb2 Lb2 Lb2 Lb
+L L L L L Lx.
+\& \& \& Bits \&
+Year System Arch Color Char Notes
+_
+1992 Solaris 5.2 32 6 17 SVr4 \fIcurses\fP
+1992 HP-UX 9 32 no 8 SVr2 \fIcurses\fP
+1992 AIX 3.2 32 no 23 SVr2 \fIcurses\fP
+1994 OSF/1 r3 32 no 23 SVr2 \fIcurses\fP
+1995 HP-UX 10.00 32 6 16 SVr3 \fIcurses_colr\fP
+1995 HP-UX 10.00 32 6 8 SVr4, X/Open \fIcurses\fP
+1995 Solaris 5.4 32/64 7 16 X/Open \fIcurses\fP
+1996 AIX 4.2 32 7 16 X/Open \fIcurses\fP
+1996 OSF/1 r4 32 6 16 X/Open \fIcurses\fP
+1997 HP-UX 11.00 32 6 8 X/Open \fIcurses\fP
+2000 U/Win 32/64 7/31 16 uses \fIchtype\fP
+.TE
+.PP
+Notes:
+.RS 3
+.PP
+Regarding HP-UX,
+.bP
+HP-UX 10.20 (1996) added support for 64-bit PA-RISC processors in 1996.
+.bP
+HP-UX 10.30 (1997) marked \*(``curses_colr\*('' obsolete.
+That version of curses was dropped with HP-UX 11.30 in 2006.
+.PP
+Regarding OSF/1 (and Tru64),
+.bP
+These used 64-bit hardware.
+Like \fI\%ncurses\fP,
+the OSF/1 curses interface is not customized for 32-bit and 64-bit
+versions.
+.bP
+Unlike other systems which evolved from AT&T code,
+OSF/1 provided a new implementation for X/Open curses.
+.PP
+Regarding Solaris,
+.bP
+The initial release of Solaris was in 1992.
+.bP
+The \fIxpg4\fP (X/Open) curses was developed by MKS from 1990 to 1995.
+Sun's copyright began in 1996.
+.bP
+Sun updated the X/Open curses interface
+after 64-bit support was introduced in 1997,
+but did not modify the SVr4 curses interface.
+.PP
+Regarding U/Win,
+.bP
+Development of the curses library began in 1991, stopped in 2000.
+.bP
+Color support was added in 1998.
+.bP
+The library uses only \fBchtype\fP (no \fBcchar_t\fP).
+.RE
+.PP
+Once X/Open curses was adopted in the mid-1990s, the constraint of
+a 32-bit interface with many colors and wide-characters for \fBchtype\fP
+became a moot point.
+The \fBcchar_t\fP structure (whose size and
+members are not specified in X/Open Curses) could be extended as needed.
+.PP
+Other interfaces are rarely used now:
+.bP
+BSD curses was improved slightly in 1993/1994 using Keith Bostic's
+modification to make the library 8-bit clean for \fBnvi\fP(1).
+He moved \fIstandout\fP attribute to a structure member.
+.IP
+The resulting 4.4BSD curses was replaced by \fI\%ncurses\fP over the
+next ten years.
+.bP
+U/Win is rarely used now.
+.\" ---------------------------------------------------------------------------