+.PP
+The strings returned by \fBunctrl\fR in this implementation are determined
+at compile time,
+showing C1 controls from the upper-128 codes with a `~' prefix rather than `^'.
+Other implementations have different conventions.
+For example, they may show both sets of control characters with `^',
+and strip the parameter to 7 bits.
+Or they may ignore C1 controls and treat all of the upper-1280 codes as
+printable.
+This implementation uses 8 bits but does not modify the string to reflect
+locale.
+The \fBuse_legacy_coding\fP function allows the caller to
+change the output of \fBunctrl\fP.
+.PP
+The \fBkeyname\fP function may return the names of user-defined
+string capabilities which are defined in the terminfo entry via the \fB-x\fP
+option of \fBtic\fP.
+This implementation automatically assigns at run-time keycodes to
+user-defined strings which begin with "k".
+The keycodes start at KEY_MAX, but are not guaranteed to be
+the same value for different runs because user-defined codes are
+merged from all terminal descriptions which have been loaded.
+.PP
+The \fBnofilter\fP routine is specific to ncurses.
+It was not supported on Version 7, BSD or System V implementations.
+It is recommended that any code depending on ncurses extensions
+be conditioned using NCURSES_VERSION.