+\fBTABSIZE\fP is a feature of SVr4 curses
+which is not documented by X/Open curses.
+.bP
+In SVr4 curses, \fBTABSIZE\fP is initially set from the terminal description's
+\fBinit_tabs\fP capability.
+After that, it can be altered by the applications using SVr4 curses.
+.IP
+SVr4 curses uses the current value of \fBTABSIZE\fP to
+compute the position of tabstops for updating both
+the virtual screen with \fBaddch\fP(3X) as well as
+the physical screen with \fBmvcur\fP(3X).
+.bP
+This implementation uses the current value of \fBTABSIZE\fP only for
+updating the virtual screen.
+It uses the terminal description's \fBit\fP (\fBinit_tabs\fP) capability for
+computing hardware tabs (i.e., tab stops on the physical screen).
+.bP
+Other implementations differ.
+For instance, NetBSD curses allows \fBTABSIZE\fP to be set through
+an environment variable.
+This implementation does not.
+.IP
+NetBSD curses does not support hardware tabs;
+it uses the \fBinit_tabs\fP capability and the \fBTABSIZE\fP variable
+only for updating the virtual screen.
+.PP
+\fBESCDELAY\fP is an extension in AIX curses:
+.bP
+In AIX, the units for \fBESCDELAY\fP are \fIfifths\fP of a millisecond.
+.bP
+The default value for AIX's \fBESCDELAY\fP is 0.1 seconds.
+.bP
+AIX also enforces a limit of 10,000 seconds for \fBESCDELAY\fP;
+this implementation currently has no upper limit.
+.PP
+This implementation has long used \fBESCDELAY\fP with units of milliseconds,
+making it impossible to be completely compatible with AIX.
+Likewise, most users have either decided to override the value,
+or rely upon its default value.