diff --git a/qse/configure b/qse/configure
index 8a3edcb8..1a864cf3 100755
--- a/qse/configure
+++ b/qse/configure
@@ -21652,7 +21652,8 @@ fi
 
 
 
-for ac_header in stddef.h wchar.h wctype.h errno.h sys/syscall.h
+
+for ac_header in stddef.h wchar.h wctype.h errno.h signal.h sys/syscall.h
 do
 as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
 if { as_var=$as_ac_Header; eval "test \"\${$as_var+set}\" = set"; }; then
diff --git a/qse/configure.ac b/qse/configure.ac
index c2ed18c1..5355bde3 100644
--- a/qse/configure.ac
+++ b/qse/configure.ac
@@ -83,7 +83,7 @@ AC_SUBST(LIBM, $LIBM)
 
 dnl check header files.
 AC_HEADER_STDC
-AC_CHECK_HEADERS([stddef.h wchar.h wctype.h errno.h sys/syscall.h])
+AC_CHECK_HEADERS([stddef.h wchar.h wctype.h errno.h signal.h sys/syscall.h])
 
 dnl check data types
 AC_CHECK_TYPE([wchar_t], 
diff --git a/qse/doc/page/cmn.doc b/qse/doc/page/cmn.doc
new file mode 100644
index 00000000..d845a09a
--- /dev/null
+++ b/qse/doc/page/cmn.doc
@@ -0,0 +1,5 @@
+/** @page cmn COMMON FUNCTIONS
+
+@section rex REGULAR EXPRESSION
+QSE provides regular expression handling functions.
+*/
diff --git a/qse/doc/page/main.doc b/qse/doc/page/main.doc
index 010d41bc..c4b3ac4b 100644
--- a/qse/doc/page/main.doc
+++ b/qse/doc/page/main.doc
@@ -94,7 +94,4 @@ on each module.
 - @subpage sed "SED Stream Editor"
 - @subpage awk "AWK Interpreter"
 
-@section design_model DESIGN MODEL
-The design of a data structure is derived from object-oriented model.
-<<MORE>>>
 */
diff --git a/qse/doc/page/sed.doc b/qse/doc/page/sed.doc
index 5d0337be..91af0e4c 100644
--- a/qse/doc/page/sed.doc
+++ b/qse/doc/page/sed.doc
@@ -1,11 +1,70 @@
-/** @page sed SED
+/** @page sed SED STREAM EDITOR
 
-STREAM EDITOR
-a stream editor is provided
+@section sed_intro INTRODUCTION
 
-@section COMMAND
-- : label  label for b and t commands. a label can be composed of an 
-           alpha-numeric character, an underscope, and an underline.
+The sed stream editor is a non-interactive text editing tool commonly used
+on Unix environment. Sed reads text from an input stream, applies a set of 
+editing commands, and writes the results to an output stream. Typically, 
+the input and output streams are a console or a file. 
+
+@b QSE provides an embeddable stream editor that supports most of 
+the conventional sed commands and implements input and output streams as a 
+callback function: 
+
+- #qse_sed_t - C type that encapsulates a stream editor
+- QSE::Sed - C++ class that wraps #qse_sed_t
+- QSE::StdSed - C++ child class of QSE::Sed that implements standard input and output streams
+
+@section sed_command COMMAND
+
+A sed command is composed of:
+
+- line selector (optional)
+- ! (optional)
+- command code
+- command arguments (optional, dependent on command code)
+
+A line selector selects input lines to apply a command to and has the following
+forms:
+- address - specify a single address
+- address,address - specify an address range 
+- start~step - specify a starting line and a step
+
+An @b address is a line number, a regular expression, or a dollar sign ($) 
+while a @b start and a @b step is a line number. 
+
+A regular expression for an address has the following form:
+- /rex/ - a regular expression @b rex is enclosed in slashes
+- \\CrexC - a regular expression @b rex is enclosed in @b \\C and @b C 
+            where @b C can be any character.
+
+It treats the @b \\n sequence specially to match a newline character.
+
+Here are examples of line selectors:
+- 10 - match the 10th line
+- 10,20 - match lines from the 10th to the 20th.
+- /^[[:space:]]*$/ - match an empty line 
+- /^abc$/,/^def$/ - match all lines between @b abc and @b def inclusive
+- 10,$ - match the 10th line down to the last line.
+- 3~4 - match every 4th line from the 3rd line.
+
+Note that an address range always selects the line matching the first address
+regardless of the second address; For example, 8,6 selects the 8th line.
+
+The exclamation mark @b !, when used after the line selector and before
+the command code, negates the line selection; For example, 1! selects all
+lines except the first line.
+
+A command without a line selector is applied to all input lines; 
+A command with a single address is applied to an input line that matches 
+the address; A command with an address range is applied to all input 
+lines within the range, inclusive; A command with a starting line and 
+a step is applied to every @b step'th line starting from the line @b start.
+
+Here is the summary of the commands.
+
+- : label  label for b and t commands. a label can be composed of letters,
+           digits, periods, hyphens, and underlines.
 - # comment
 - = print the current line number
 */
diff --git a/qse/include/qse/config.h.in b/qse/include/qse/config.h.in
index ad53568b..93fa4514 100644
--- a/qse/include/qse/config.h.in
+++ b/qse/include/qse/config.h.in
@@ -87,6 +87,9 @@
 /* Define to 1 if you have the `powl' function. */
 #undef HAVE_POWL
 
+/* Define to 1 if you have the <signal.h> header file. */
+#undef HAVE_SIGNAL_H
+
 /* Define to 1 if you have the `sin' function. */
 #undef HAVE_SIN
 
diff --git a/qse/lib/cmn/assert.c b/qse/lib/cmn/assert.c
index 675b7e10..c4d3ee9a 100644
--- a/qse/lib/cmn/assert.c
+++ b/qse/lib/cmn/assert.c
@@ -22,7 +22,50 @@
 #ifndef NDEBUG
 
 #include <qse/cmn/sio.h>
-#include <stdlib.h>
+
+#ifdef _WIN32
+#       include <windows.h>
+#else
+#	include "syscall.h"
+#endif
+
+#define NTOC(n) (((n) >= 10)? (((n) - 10) + QSE_T('A')): (n) + QSE_T('0'))
+#define WRITE_CHAR(c) \
+do { \
+	qse_char_t __xxx_c = c; \
+	if (qse_sio_putsn (QSE_SIO_ERR, &__xxx_c, 1) != 1) return -1; \
+} while (0)
+
+static int write_num (qse_size_t x, int base)
+{
+	qse_size_t last = x % base;
+	qse_size_t y = 0; 
+	int dig = 0;
+
+	x = x / base;
+
+	while (x > 0)
+	{
+		y = y * base + (x % base);
+		x = x / base;
+		dig++;
+	}
+
+	while (y > 0)
+	{
+		WRITE_CHAR (NTOC(y % base));
+		y = y / base;
+		dig--;
+	}
+
+	while (dig > 0) 
+	{ 
+		dig--; 
+		WRITE_CHAR (QSE_T('0'));
+	}
+	WRITE_CHAR (NTOC(last));
+	return 0;
+}
 
 void qse_assert_failed (
 	const qse_char_t* expr, const qse_char_t* desc, 
@@ -32,9 +75,9 @@ void qse_assert_failed (
 
 	qse_sio_puts (QSE_SIO_ERR, QSE_T("FILE "));
 	qse_sio_puts (QSE_SIO_ERR, file);
-	qse_sio_puts (QSE_SIO_ERR, QSE_T("LINE "));
+	qse_sio_puts (QSE_SIO_ERR, QSE_T(" LINE "));
 
-/*qse_sio_puts the number */
+	write_num (line, 10);
 
 	qse_sio_puts (QSE_SIO_ERR, QSE_T(": "));
 	qse_sio_puts (QSE_SIO_ERR, expr);
@@ -47,8 +90,14 @@ void qse_assert_failed (
 		qse_sio_puts (QSE_SIO_ERR, QSE_T("\n"));
 	}
 	qse_sio_puts (QSE_SIO_ERR, QSE_T("================================================================================"));
+	qse_sio_flush (QSE_SIO_ERR);
 
-	abort ();
+#ifdef _WIN32
+	ExitProcess (1);
+#else
+	QSE_KILL (QSE_GETPID(), SIGABRT);
+	QSE_EXIT (1);
+#endif
 }
 
 #endif
diff --git a/qse/lib/sed/sed.c b/qse/lib/sed/sed.c
index 779cb370..95fb3a90 100644
--- a/qse/lib/sed/sed.c
+++ b/qse/lib/sed/sed.c
@@ -2676,7 +2676,7 @@ int qse_sed_exec (qse_sed_t* sed, qse_sed_io_fun_t inf, qse_sed_io_fun_t outf)
 				if (c->negated) n = !n;
 				if (n == 0)
 				{
-					c++;
+					c = c->state.next;
 					continue;
 				}