+.SS bool, TRUE, FALSE
+X/Open Issue 4 \fIcurses\fP (1996) preceded the ISO C99 and ISO C++98
+standards,
+each of which also defined a Boolean data type.
+The \fIcurses\fP library requires an integral type \fIbool\fP and
+constants \fBTRUE\fP and \fBFALSE\fP to store its two possible values.
+.SS ERR, OK
+\fIcurses\fP and \fIterminfo\fP routines frequently return these
+constant integral values indicating failure and success,
+respectively.
+.SS chtype
+The \fI\%chtype\fP integral type combines a
+(\*(``narrow\*('',
+8-bit)
+character with attributes encoding the character's \fIrendition\fP,
+such as the styling of its typeface and/or foreground and background
+colors.
+See,
+for example,
+\fB\%addch\fP(3X),
+\fB\%attron\fP(3X),
+and
+\fB\%inch\fP(3X).
+.SS cchar_t, attr_t
+\fI\%chtype\fP is too small for the standard C library's wide-character
+type,
+\fIwchar_t\fP.
+\fI\%cchar_t\fP is a type that can accommodate an \fI\%attr_t\fP and
+enough wide characters to store what Unicode terms a \fIgrapheme cluster\fP
+(a \*(``user-perceived character\*('' [UAX #29],
+which may nevertheless require several character encoding units to
+represent).
+\fI\%attr_t\fP is an integral type storing \*(``wide\*('' attributes that
+apply to \fI\%cchar_t\fPs.
+See,
+for example,
+\fB\%add_wch\fP(3X),
+\fB\%attr_on\fP(3X),
+and
+\fB\%in_wch\fP(3X).