diff --git a/stix/kernel/Apex.st b/stix/kernel/Apex.st
index c6af017..2a5d390 100644
--- a/stix/kernel/Apex.st
+++ b/stix/kernel/Apex.st
@@ -332,10 +332,39 @@
 	}
 }
 
+(* --------------------
+#pooldic Error
+{
+	#NONE := error(0).
+	#GENERIC := error(1).
+	#
+}
+------------------- *)
+
 #class Error(Apex)
 {
+	(* ----------------------------
+	TODO: support constant declaration...
+
+	#const
+	{
+		#NONE := error(0).
+		#GENERIC := error(1).
+	}
+	-------------------------------- *)
+
 	#method isError
 	{
 		^true
 	}
+
+	#method asInteger
+	{
+		<primitive: #_error_as_integer>
+	}
+
+	#method asString
+	{
+		<primitive: #_error_as_string>
+	}
 }
diff --git a/stix/kernel/generr.st b/stix/kernel/generr.st
new file mode 100644
index 0000000..62345de
--- /dev/null
+++ b/stix/kernel/generr.st
@@ -0,0 +1,85 @@
+#include 'Stix.st'.
+
+#class MyObject(Object)
+{
+
+	#method(#class) main
+	{
+		| s c f |
+
+		s := #( 
+			'no error'
+			'generic error'
+
+			'not implemented'
+			'subsystem error'
+			'internal error that should never have happened'
+
+			'insufficient system memory'
+			'insufficient object memory'
+
+			'invalid parameter or argument'
+			'data not found'
+			'existing/duplicate data'
+			'busy'
+			'access denied'
+			'operation not permitted'
+			'not a directory'
+			'interrupted'
+			'pipe error'
+			'resource temporarily unavailable'
+
+			'data too large'
+			'message sending error'
+			'range error'
+			'byte-code full'
+			'dictionary full'
+			'processor full'
+			'semaphore heap full'
+			'semaphore list full'
+			'divide by zero'
+			'I/O error'
+			'encoding conversion error'
+		).
+
+		f := Stdio open: 'generr.out' for: 'w'.
+		[ f isError ] ifTrue: [ System logNl: 'Cannot open generr.out'. thisProcess terminate. ].
+
+		c := s size - 1.
+		0 to: c do: [:i |
+			self printString: (s at: i) index: i on: f.
+		].
+
+		f puts: S'static stix_ooch_t* errstr[] =\n{\n'.
+		0 to: c do: [:i |
+			((i rem: 8) = 0) ifTrue: [ f putc: C'\t' ].
+			f puts: S'e'.
+			f puts: (i asString).
+			(i = c) ifFalse: [f puts: S',' ].
+			(((i  + 1) rem: 8) = 0) ifTrue: [ f putc: C'\n' ] ifFalse: [ f putc: C' ' ].
+		].
+		(((c + 1) rem: 8) = 0) ifFalse: [ f putc: C'\n' ].
+		f puts: S'};\n'.
+
+		f close.
+	}
+
+	#method(#class) printString: s index: index on: f
+	{
+		| c  |
+		c := s size - 1.
+
+		f puts: 'static stix_ooch_t e'.
+		f puts: index asString.
+		f puts: '[] = {'.
+
+		0 to: c do: [:i |
+			f putc: $'.
+			f putc: (s at: i).
+			f putc: $'.
+			(i = c) ifFalse: [f putc: $, ].
+		].
+
+		f puts: S',\'\\0\'};\n'.
+	}
+}
diff --git a/stix/kernel/test-014.st b/stix/kernel/test-014.st
index ec2036b..499cb1c 100644
--- a/stix/kernel/test-014.st
+++ b/stix/kernel/test-014.st
@@ -125,17 +125,16 @@
 
 
 		##v1 := Stdio2 open: '/tmp/1.txt' for: 'w+'.
-		v1 := Stdio2 new open: '/tmp/1.txt' for: 'w+'.
+		v1 := Stdio2 new open: '/tmp/x/1.txt' for: 'w+'.
 		(v1 isError) 
 			ifTrue: [
-				System logNl: ('Error in opening a file....').
+				System logNl: ('Error in opening a file....' & v1 asString). 
 			]
 			ifFalse: [
 				## v1 puts: 'hello'.
 				v1 puts ('hello', 'world', 'good', C'\n', C'\t', 'under my umbrella.', C'\n').
 				v1 close.
 
-
 				(*v1 format(10, 20) isNil ifFalse: [
 				 	'Beautiful life' dump.
 				].*)
diff --git a/stix/lib/Makefile.am b/stix/lib/Makefile.am
index 775836f..18e5653 100644
--- a/stix/lib/Makefile.am
+++ b/stix/lib/Makefile.am
@@ -42,6 +42,7 @@ libstix_la_SOURCES = \
 	debug.c  \
 	decode.c \
 	dic.c \
+	err.c \
 	exec.c \
 	logfmtv.h \
 	logfmt.c \
diff --git a/stix/lib/Makefile.in b/stix/lib/Makefile.in
index c83aa18..95e6490 100644
--- a/stix/lib/Makefile.in
+++ b/stix/lib/Makefile.in
@@ -136,10 +136,10 @@ am__DEPENDENCIES_2 = $(am__DEPENDENCIES_1) $(am__DEPENDENCIES_1)
 libstix_la_DEPENDENCIES = $(am__DEPENDENCIES_2)
 am_libstix_la_OBJECTS = libstix_la-bigint.lo libstix_la-comp.lo \
 	libstix_la-debug.lo libstix_la-decode.lo libstix_la-dic.lo \
-	libstix_la-exec.lo libstix_la-logfmt.lo libstix_la-gc.lo \
-	libstix_la-heap.lo libstix_la-obj.lo libstix_la-proc.lo \
-	libstix_la-rbt.lo libstix_la-stix.lo libstix_la-sym.lo \
-	libstix_la-utf8.lo libstix_la-utl.lo
+	libstix_la-err.lo libstix_la-exec.lo libstix_la-logfmt.lo \
+	libstix_la-gc.lo libstix_la-heap.lo libstix_la-obj.lo \
+	libstix_la-proc.lo libstix_la-rbt.lo libstix_la-stix.lo \
+	libstix_la-sym.lo libstix_la-utf8.lo libstix_la-utl.lo
 libstix_la_OBJECTS = $(am_libstix_la_OBJECTS)
 AM_V_lt = $(am__v_lt_@AM_V@)
 am__v_lt_ = $(am__v_lt_@AM_DEFAULT_V@)
@@ -409,6 +409,7 @@ libstix_la_SOURCES = \
 	debug.c  \
 	decode.c \
 	dic.c \
+	err.c \
 	exec.c \
 	logfmtv.h \
 	logfmt.c \
@@ -582,6 +583,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libstix_la-debug.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libstix_la-decode.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libstix_la-dic.Plo@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libstix_la-err.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libstix_la-exec.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libstix_la-gc.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/libstix_la-heap.Plo@am__quote@
@@ -654,6 +656,13 @@ libstix_la-dic.lo: dic.c
 @AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
 @am__fastdepCC_FALSE@	$(AM_V_CC@am__nodep@)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(libstix_la_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -c -o libstix_la-dic.lo `test -f 'dic.c' || echo '$(srcdir)/'`dic.c
 
+libstix_la-err.lo: err.c
+@am__fastdepCC_TRUE@	$(AM_V_CC)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(libstix_la_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -MT libstix_la-err.lo -MD -MP -MF $(DEPDIR)/libstix_la-err.Tpo -c -o libstix_la-err.lo `test -f 'err.c' || echo '$(srcdir)/'`err.c
+@am__fastdepCC_TRUE@	$(AM_V_at)$(am__mv) $(DEPDIR)/libstix_la-err.Tpo $(DEPDIR)/libstix_la-err.Plo
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	$(AM_V_CC)source='err.c' object='libstix_la-err.lo' libtool=yes @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCC_FALSE@	$(AM_V_CC@am__nodep@)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(libstix_la_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -c -o libstix_la-err.lo `test -f 'err.c' || echo '$(srcdir)/'`err.c
+
 libstix_la-exec.lo: exec.c
 @am__fastdepCC_TRUE@	$(AM_V_CC)$(LIBTOOL) $(AM_V_lt) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(libstix_la_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -MT libstix_la-exec.lo -MD -MP -MF $(DEPDIR)/libstix_la-exec.Tpo -c -o libstix_la-exec.lo `test -f 'exec.c' || echo '$(srcdir)/'`exec.c
 @am__fastdepCC_TRUE@	$(AM_V_at)$(am__mv) $(DEPDIR)/libstix_la-exec.Tpo $(DEPDIR)/libstix_la-exec.Plo
diff --git a/stix/lib/comp.c b/stix/lib/comp.c
index 7e9479a..66bd51b 100644
--- a/stix/lib/comp.c
+++ b/stix/lib/comp.c
@@ -81,6 +81,7 @@ static struct voca_t
 	{  4, { '#','d','c','l'                                               } },
 	{  8, { '#','d','e','c','l','a','r','e'                               } },
 	{  6, { 'e','n','s','u','r','e',                                      } },
+	{  5, { 'e','r','r','o','r'                                           } },
 	{  9, { 'e','x','c','e','p','t','i','o','n'                           } },
 	{  7, { '#','e','x','t','e','n','d'                                   } },
 	{  5, { 'f','a','l','s','e'                                           } },
@@ -118,6 +119,7 @@ enum voca_id_t
 	VOCA_DCL,
 	VOCA_DECLARE,
 	VOCA_ENSURE,
+	VOCA_ERROR,
 	VOCA_EXCEPTION,
 	VOCA_EXTEND,
 	VOCA_FALSE,
@@ -264,8 +266,9 @@ static int is_reserved_word (const stix_oocs_t* ucs)
 		VOCA_NIL,
 		VOCA_TRUE,
 		VOCA_FALSE,
+		VOCA_ERROR,
 		VOCA_THIS_CONTEXT,
-		VOCA_THIS_PROCESS
+		VOCA_THIS_PROCESS,
 	};
 	int i;
 
diff --git a/stix/lib/err.c b/stix/lib/err.c
new file mode 100644
index 0000000..02d5e24
--- /dev/null
+++ b/stix/lib/err.c
@@ -0,0 +1,165 @@
+/*
+ * $Id$
+ *
+    Copyright (c) 2014-2016 Chung, Hyung-Hwan. All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions
+    are met:
+    1. Redistributions of source code must retain the above copyright
+       notice, this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright
+       notice, this list of conditions and the following disclaimer in the
+       documentation and/or other materials provided with the distribution.
+
+    THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR
+    IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+    OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+    IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+    NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+    THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "stix-prv.h"
+
+
+
+/* BEGIN: GENERATED WITH generr.st */
+
+static stix_ooch_t e0[] = {'n','o',' ','e','r','r','o','r','\0'};
+static stix_ooch_t e1[] = {'g','e','n','e','r','i','c',' ','e','r','r','o','r','\0'};
+static stix_ooch_t e2[] = {'n','o','t',' ','i','m','p','l','e','m','e','n','t','e','d','\0'};
+static stix_ooch_t e3[] = {'s','u','b','s','y','s','t','e','m',' ','e','r','r','o','r','\0'};
+static stix_ooch_t e4[] = {'i','n','t','e','r','n','a','l',' ','e','r','r','o','r',' ','t','h','a','t',' ','s','h','o','u','l','d',' ','n','e','v','e','r',' ','h','a','v','e',' ','h','a','p','p','e','n','e','d','\0'};
+static stix_ooch_t e5[] = {'i','n','s','u','f','f','i','c','i','e','n','t',' ','s','y','s','t','e','m',' ','m','e','m','o','r','y','\0'};
+static stix_ooch_t e6[] = {'i','n','s','u','f','f','i','c','i','e','n','t',' ','o','b','j','e','c','t',' ','m','e','m','o','r','y','\0'};
+static stix_ooch_t e7[] = {'i','n','v','a','l','i','d',' ','p','a','r','a','m','e','t','e','r',' ','o','r',' ','a','r','g','u','m','e','n','t','\0'};
+static stix_ooch_t e8[] = {'d','a','t','a',' ','n','o','t',' ','f','o','u','n','d','\0'};
+static stix_ooch_t e9[] = {'e','x','i','s','t','i','n','g','/','d','u','p','l','i','c','a','t','e',' ','d','a','t','a','\0'};
+static stix_ooch_t e10[] = {'b','u','s','y','\0'};
+static stix_ooch_t e11[] = {'a','c','c','e','s','s',' ','d','e','n','i','e','d','\0'};
+static stix_ooch_t e12[] = {'o','p','e','r','a','t','i','o','n',' ','n','o','t',' ','p','e','r','m','i','t','t','e','d','\0'};
+static stix_ooch_t e13[] = {'n','o','t',' ','a',' ','d','i','r','e','c','t','o','r','y','\0'};
+static stix_ooch_t e14[] = {'i','n','t','e','r','r','u','p','t','e','d','\0'};
+static stix_ooch_t e15[] = {'p','i','p','e',' ','e','r','r','o','r','\0'};
+static stix_ooch_t e16[] = {'r','e','s','o','u','r','c','e',' ','t','e','m','p','o','r','a','r','i','l','y',' ','u','n','a','v','a','i','l','a','b','l','e','\0'};
+static stix_ooch_t e17[] = {'d','a','t','a',' ','t','o','o',' ','l','a','r','g','e','\0'};
+static stix_ooch_t e18[] = {'m','e','s','s','a','g','e',' ','s','e','n','d','i','n','g',' ','e','r','r','o','r','\0'};
+static stix_ooch_t e19[] = {'r','a','n','g','e',' ','e','r','r','o','r','\0'};
+static stix_ooch_t e20[] = {'b','y','t','e','-','c','o','d','e',' ','f','u','l','l','\0'};
+static stix_ooch_t e21[] = {'d','i','c','t','i','o','n','a','r','y',' ','f','u','l','l','\0'};
+static stix_ooch_t e22[] = {'p','r','o','c','e','s','s','o','r',' ','f','u','l','l','\0'};
+static stix_ooch_t e23[] = {'s','e','m','a','p','h','o','r','e',' ','h','e','a','p',' ','f','u','l','l','\0'};
+static stix_ooch_t e24[] = {'s','e','m','a','p','h','o','r','e',' ','l','i','s','t',' ','f','u','l','l','\0'};
+static stix_ooch_t e25[] = {'d','i','v','i','d','e',' ','b','y',' ','z','e','r','o','\0'};
+static stix_ooch_t e26[] = {'I','/','O',' ','e','r','r','o','r','\0'};
+static stix_ooch_t e27[] = {'e','n','c','o','d','i','n','g',' ','c','o','n','v','e','r','s','i','o','n',' ','e','r','r','o','r','\0'};
+static stix_ooch_t* errstr[] =
+{
+	e0, e1, e2, e3, e4, e5, e6, e7,
+	e8, e9, e10, e11, e12, e13, e14, e15,
+	e16, e17, e18, e19, e20, e21, e22, e23,
+	e24, e25, e26, e27 
+};
+
+/* END: GENERATED WITH generr.st */
+
+/* -------------------------------------------------------------------------- 
+ * ERROR NUMBER TO STRING CONVERSION
+ * -------------------------------------------------------------------------- */
+const stix_ooch_t* stix_errnumtoerrstr (stix_errnum_t errnum)
+{
+	static stix_ooch_t e_unknown[] = {'u','n','k','n','o','w','n',' ','e','r','r','o','r','\0'};
+	return (errnum >= 0 && errnum < STIX_COUNTOF(errstr))? errstr[errnum]: e_unknown;
+}
+
+/* -------------------------------------------------------------------------- 
+ * SYSTEM DEPENDENT FUNCTIONS 
+ * -------------------------------------------------------------------------- */
+
+#if defined(_WIN32)
+#	include <windows.h>
+#elif defined(__OS2__)
+#	define INCL_DOSPROCESS
+#	define INCL_DOSFILEMGR
+#	include <os2.h>
+#elif defined(__DOS__)
+#	include <dos.h>
+#	include <dosfunc.h>
+#elif defined(vms) || defined(__vms)
+#	define __NEW_STARLET 1
+#	include <starlet.h> /* (SYS$...) */
+#	include <ssdef.h> /* (SS$...) */
+#	include <lib$routines.h> /* (lib$...) */
+#elif defined(macintosh)
+#	include <Process.h>
+#	include <Dialogs.h>
+#	include <TextUtils.h>
+#else
+#	include <sys/types.h>
+#	include <unistd.h>
+#	include <signal.h>
+#	include <errno.h>
+#endif
+
+stix_errnum_t stix_syserrtoerrnum (int e)
+{
+	switch (e)
+	{
+		case ENOMEM: return STIX_ESYSMEM;
+		case EINVAL: return STIX_EINVAL;
+		case EBUSY: return STIX_EBUSY;
+		case EACCES: return STIX_EACCES;
+		case EPERM: return STIX_EPERM;
+		case ENOTDIR: return STIX_ENOTDIR;
+		case ENOENT: return STIX_ENOENT;
+		case EEXIST: return STIX_EEXIST;
+		case EINTR:  return STIX_EINTR;
+		case EPIPE:  return STIX_EPIPE;
+	#if defined(EAGAIN) && defined(EWOULDBLOCK) && (EAGAIN != EWOULDBLOCK)
+		case EAGAIN: 
+		case EWOULDBLOCK: return STIX_EAGAIN;
+	#elif defined(EAGAIN)
+		case EAGAIN: return STIX_EAGAIN;
+	#elif defined(EWOULDBLOCK)
+		case EWOULDBLOCK: return STIX_EAGAIN;
+	#endif
+		default:     return STIX_ESYSERR;
+	}
+}
+
+/* -------------------------------------------------------------------------- 
+ * ASSERTION FAILURE HANDLER
+ * -------------------------------------------------------------------------- */
+
+void stix_assertfailed (stix_t* stix, const stix_bch_t* expr, const stix_bch_t* file, stix_oow_t line)
+{
+	stix_logbfmt (stix, STIX_LOG_DEBUG, "ASSERTION FAILURE: %s at %s:%zu\n", expr, file, line);
+
+#if defined(_WIN32)
+	ExitProcess (249);
+#elif defined(__OS2__)
+	DosExit (EXIT_PROCESS, 249);
+#elif defined(__DOS__)
+	{
+		union REGS regs;
+		regs.h.ah = DOS_EXIT;
+		regs.h.al = 249;
+		intdos (&regs, &regs);
+	}
+#elif defined(vms) || defined(__vms)
+	lib$stop (SS$_ABORT); /* use SS$_OPCCUS instead? */
+	/* this won't be reached since lib$stop() terminates the process */
+	sys$exit (SS$_ABORT); /* this condition code can be shown with
+	                       * 'show symbol $status' from the command-line. */
+#elif defined(macintosh)
+	ExitToShell ();
+#else
+	kill (getpid(), SIGABRT);
+	_exit (1);
+#endif
+}
diff --git a/stix/lib/exec.c b/stix/lib/exec.c
index b67b56c..be4f75d 100644
--- a/stix/lib/exec.c
+++ b/stix/lib/exec.c
@@ -2409,26 +2409,46 @@ static int pf_integer_inttostr (stix_t* stix, stix_ooi_t nargs)
 	return 1;
 }
 
-static int pf_error_as_string (stix_t* stix, stix_ooi_t nargs)
+static int pf_error_as_integer (stix_t* stix, stix_ooi_t nargs)
 {
-	stix_oop_t rcv, str;
+	stix_oop_t rcv;
+	stix_ooi_t ec;
 
 	STIX_ASSERT (stix, nargs == 0);
 
 	rcv = STIX_STACK_GETRCV(stix, nargs);
 	if (!STIX_OOP_IS_ERROR(rcv)) return 0;
 
-	//str = stix_makestring (stix, xxx, xxx);
-	STIX_STACK_SETRET (stix, nargs, str);
+	ec = STIX_OOP_TO_ERROR(rcv);
+	STIX_ASSERT (stix, STIX_IN_SMOOI_RANGE(ec));
+	STIX_STACK_SETRET (stix, nargs, STIX_SMOOI_TO_OOP(ec));
 	return 1;
 }
 
-static int pf_error_text (stix_t* stix, stix_ooi_t nargs)
+static int pf_error_as_string (stix_t* stix, stix_ooi_t nargs)
 {
+	stix_oop_t rcv, ss;
+	stix_ooi_t ec;
+	const stix_ooch_t* s;
 
-	return -1;
+	STIX_ASSERT (stix, nargs == 0);
+
+	rcv = STIX_STACK_GETRCV(stix, nargs);
+	if (!STIX_OOP_IS_ERROR(rcv)) return 0;
+
+	ec = STIX_OOP_TO_ERROR(rcv);
+	STIX_ASSERT (stix, STIX_IN_SMOOI_RANGE(ec));
+
+/* TODO: error string will be mostly the same.. do i really have to call makestring every time? */
+	s = stix_errnumtoerrstr (ec);
+	ss = stix_makestring (stix, s, stix_countoocstr(s));
+	if (!ss) return -1;
+
+	STIX_STACK_SETRET (stix, nargs, ss);
+	return 1;
 }
 
+
 static int pf_ffi_open (stix_t* stix, stix_ooi_t nargs)
 {
 	stix_oop_t rcv, arg;
@@ -2586,7 +2606,7 @@ STIX_DEBUG2 (stix, "CALL MODE 222 ERROR %d %d\n", dcGetError (dc), DC_ERROR_UNSU
 					stix_bch_t bcs[1024];
 
 					ucslen = STIX_OBJ_GET_SIZE(arr->slot[i - 2]);
-					stix_oocstobcs (stix, ((stix_oop_char_t)arr->slot[i - 2])->slot, &ucslen, bcs, &bcslen); /* proper string conversion */
+					stix_convootobchars (stix, ((stix_oop_char_t)arr->slot[i - 2])->slot, &ucslen, bcs, &bcslen); /* proper string conversion */
 
 					bcs[bcslen] = '\0';
 					dcArgPointer (dc, bcs);
@@ -2644,7 +2664,7 @@ STIX_DEBUG2 (stix, "CALL ERROR %d %d\n", dcGetError (dc), DC_ERROR_UNSUPPORTED_M
 				char* r = dcCallPointer (dc, f);
 
 				bcslen = strlen(r); 
-				stix_bcstooocs (stix, r, &bcslen, ucs, &ucslen); /* proper string conversion */
+				stix_convbtooochars (stix, r, &bcslen, ucs, &ucslen); /* proper string conversion */
 
 				s = stix_makestring(stix, ucs, ucslen)
 				if (!s) 
@@ -2780,8 +2800,9 @@ static pf_t pftab[] =
 	{   1,  1,  pf_integer_ge,                       "_integer_ge"          },
 	{   1,  1,  pf_integer_inttostr,                 "_integer_inttostr"    },
 
+	{   0,  0,  pf_error_as_integer,                 "_error_as_integer"    },
 	{   0,  0,  pf_error_as_string,                  "_error_as_string"     },
-	{   0,  0,  pf_error_text,                       "_error_text"          },
+
 
 	{   1,  1,  pf_ffi_open,                         "_ffi_open"            },
 	{   1,  1,  pf_ffi_close,                        "_ffi_close"           },
diff --git a/stix/lib/logfmtv.h b/stix/lib/logfmtv.h
index f8143c9..851a215 100644
--- a/stix/lib/logfmtv.h
+++ b/stix/lib/logfmtv.h
@@ -425,7 +425,7 @@ reswitch:
 			/* get the length */
 			for (bslen = 0; bsp[bslen]; bslen++);
 
-			if (stix_bcstooocs (stix, bsp, &bslen, STIX_NULL, &slen) <= -1)
+			if (stix_convbtooochars (stix, bsp, &bslen, STIX_NULL, &slen) <= -1)
 			{ 
 				/* conversion error */
 				stix->errnum = STIX_EECERR;
@@ -450,7 +450,7 @@ reswitch:
 					conv_len = STIX_COUNTOF(conv_buf);
 
 					/* this must not fail since the dry-run above was successful */
-					stix_bcstooocs (stix, &bsp[tot_len], &src_len, conv_buf, &conv_len);
+					stix_convbtooochars (stix, &bsp[tot_len], &src_len, conv_buf, &conv_len);
 					tot_len += src_len;
 
 					if (conv_len > n) conv_len = n;
diff --git a/stix/lib/main.c b/stix/lib/main.c
index dfc0912..e410920 100644
--- a/stix/lib/main.c
+++ b/stix/lib/main.c
@@ -142,9 +142,9 @@ static STIX_INLINE stix_ooi_t open_input (stix_t* stix, stix_ioarg_t* arg)
 		/* includee */
 		stix_bch_t bcs[1024]; /* TODO: right buffer size */
 		stix_oow_t bcslen = STIX_COUNTOF(bcs);
-		stix_oow_t ucslen = ~(stix_oow_t)0;
+		stix_oow_t ucslen;
 
-		if (stix_oocstobcs (stix, arg->name, &ucslen, bcs, &bcslen) <= -1)
+		if (stix_convootobcstr (stix, arg->name, &ucslen, bcs, &bcslen) <= -1)
 		{
 			stix_seterrnum (stix, STIX_EECERR);
 			return -1;
@@ -231,8 +231,8 @@ static STIX_INLINE stix_ooi_t read_input (stix_t* stix, stix_ioarg_t* arg)
 
 	bcslen = bb->len;
 	ucslen = STIX_COUNTOF(arg->buf);
-	x = stix_bcstooocs (stix, bb->buf, &bcslen, arg->buf, &ucslen);
-	x = stix_bcstooocs (stix, bb->buf, &bcslen, arg->buf, &ucslen);
+	x = stix_convbtooochars (stix, bb->buf, &bcslen, arg->buf, &ucslen);
+	x = stix_convbtooochars (stix, bb->buf, &bcslen, arg->buf, &ucslen);
 	if (x <= -1 && ucslen <= 0)
 	{
 		stix_seterrnum (stix, STIX_EECERR);
@@ -287,9 +287,8 @@ static void* dl_open (stix_t* stix, const stix_ooch_t* name)
 	len = stix_copybcstr (buf, STIX_COUNTOF(buf), STIX_DEFAULT_MODPREFIX);
 
 /* TODO: proper error checking and overflow checking */
-	ucslen = ~(stix_oow_t)0;
 	bcslen = STIX_COUNTOF(buf) - len;
-	stix_oocstobcs (stix, name, &ucslen, &buf[len], &bcslen);
+	stix_convootobcstr (stix, name, &ucslen, &buf[len], &bcslen);
 
 	stix_copybcstr (&buf[bcslen + len], STIX_COUNTOF(buf) - bcslen - len, STIX_DEFAULT_MODPOSTFIX);
 
@@ -339,9 +338,8 @@ static void* dl_getsym (stix_t* stix, void* handle, const stix_ooch_t* name)
 
 	buf[0] = '_';
 
-	ucslen = ~(stix_oow_t)0;
 	bcslen = STIX_COUNTOF(buf) - 2;
-	stix_oocstobcs (stix, name, &ucslen, &buf[1], &bcslen); /* TODO: error check */
+	stix_convootobcstr (stix, name, &ucslen, &buf[1], &bcslen); /* TODO: error check */
 	symname = &buf[1];
 	sym = lt_dlsym (handle, symname);
 	if (!sym)
@@ -436,7 +434,7 @@ if (mask & STIX_LOG_GC) return; /* don't show gc logs */
 		ucslen = len;
 		bcslen = STIX_COUNTOF(buf);
 
-		n = stix_oocstobcs (stix, &msg[msgidx], &ucslen, buf, &bcslen);
+		n = stix_convootobchars (stix, &msg[msgidx], &ucslen, buf, &bcslen);
 		if (n == 0 || n == -2)
 		{
 			/* n = 0: 
@@ -731,8 +729,7 @@ int main (int argc, char* argv[])
 				if (synerr.loc.file)
 				{
 					bcslen = STIX_COUNTOF(bcs);
-					ucslen = ~(stix_oow_t)0;
-					if (stix_oocstobcs (stix, synerr.loc.file, &ucslen, bcs, &bcslen) >= 0)
+					if (stix_convootobcstr (stix, synerr.loc.file, &ucslen, bcs, &bcslen) >= 0)
 					{
 						printf ("%.*s ", (int)bcslen, bcs);
 					}
@@ -751,7 +748,7 @@ int main (int argc, char* argv[])
 					bcslen = STIX_COUNTOF(bcs);
 					ucslen = synerr.tgt.len;
 
-					if (stix_oocstobcs (stix, synerr.tgt.ptr, &ucslen, bcs, &bcslen) >= 0)
+					if (stix_convootobchars (stix, synerr.tgt.ptr, &ucslen, bcs, &bcslen) >= 0)
 					{
 						printf (" [%.*s]", (int)bcslen, bcs);
 					}
diff --git a/stix/lib/stix-rbt.h b/stix/lib/stix-rbt.h
index a99bebb..69fc209 100644
--- a/stix/lib/stix-rbt.h
+++ b/stix/lib/stix-rbt.h
@@ -513,7 +513,7 @@ STIX_EXPORT stix_rbt_pair_t* stix_rbt_update (
 STIX_EXPORT stix_rbt_pair_t* stix_rbt_cbsert (
 	stix_rbt_t*         rbt,      /**< red-black tree */
 	void*               kptr,     /**< key pointer */
-	stix_oow_t         klen,     /**< key length */
+	stix_oow_t          klen,     /**< key length */
 	stix_rbt_cbserter_t cbserter, /**< callback function */
 	void*               ctx       /**< callback context */
 );
@@ -525,7 +525,7 @@ STIX_EXPORT stix_rbt_pair_t* stix_rbt_cbsert (
 STIX_EXPORT int stix_rbt_delete (
 	stix_rbt_t* rbt,   /**< red-black tree */
 	const void* kptr, /**< key pointer */
-	stix_oow_t klen   /**< key size */
+	stix_oow_t  klen   /**< key size */
 );
 
 /**
diff --git a/stix/lib/stix-utl.h b/stix/lib/stix-utl.h
index 5aeae88..82fc098 100644
--- a/stix/lib/stix-utl.h
+++ b/stix/lib/stix-utl.h
@@ -39,7 +39,7 @@ extern "C" {
 #	define stix_compoocbcstr(str1,str2) stix_compucbcstr(str1,str2)
 #	define stix_compoocstr(str1,str2) stix_compucstr(str1,str2)
 #	define stix_copyoochars(dst,src,len) stix_copyuchars(dst,src,len)
-#	define stix_copybctooochars(dst,src,len) stix_copybctouchars(dst,src,len)
+#	define stix_copybctooochars(dst,src,len) stix_copybtouchars(dst,src,len)
 #	define stix_copyoocstr(dst,len,src) stix_copyucstr(dst,len,src)
 #	define stix_findoochar(ptr,len,c) stix_finduchar(ptr,len,c)
 #	define stix_rfindoochar(ptr,len,c) stix_rfinduchar(ptr,len,c)
@@ -122,7 +122,7 @@ STIX_EXPORT void stix_copybchars (
 	stix_oow_t        len
 );
 
-STIX_EXPORT void stix_copybctouchars (
+STIX_EXPORT void stix_copybtouchars (
 	stix_uch_t*       dst,
 	const stix_bch_t* src,
 	stix_oow_t        len
@@ -190,7 +190,7 @@ STIX_EXPORT stix_cmgr_t* stix_getutf8cmgr (
 );
 
 /**
- * The stix_ucstoutf8() function converts a unicode character string \a ucs 
+ * The stix_convutoutf8chars() function converts a unicode character string \a ucs 
  * to a UTF8 string and writes it into the buffer pointed to by \a bcs, but
  * not more than \a bcslen bytes including the terminating null.
  *
@@ -211,14 +211,14 @@ STIX_EXPORT stix_cmgr_t* stix_getutf8cmgr (
  *   stix_bch_t bcs[10];
  *   stix_oow_t ucslen = 5;
  *   stix_oow_t bcslen = STIX_COUNTOF(bcs);
- *   n = stix_ucstoutf8 (ucs, &ucslen, bcs, &bcslen);
+ *   n = stix_convutoutf8chars (ucs, &ucslen, bcs, &bcslen);
  *   if (n <= -1)
  *   {
  *      // conversion error
  *   }
  * \endcode
  */
-STIX_EXPORT int stix_ucstoutf8 (
+STIX_EXPORT int stix_convutoutf8chars (
 	const stix_uch_t*    ucs,
 	stix_oow_t*          ucslen,
 	stix_bch_t*          bcs,
@@ -226,7 +226,7 @@ STIX_EXPORT int stix_ucstoutf8 (
 );
 
 /**
- * The stix_utf8toucs() function converts a UTF8 string to a uncide string.
+ * The stix_convutf8touchars() function converts a UTF8 string to a uncide string.
  *
  * It never returns -2 if \a ucs is #STIX_NULL.
  *
@@ -236,13 +236,9 @@ STIX_EXPORT int stix_ucstoutf8 (
  *  stix_oow_t ucslen = STIX_COUNTOF(buf), n;
  *  stix_oow_t bcslen = 11;
  *  int n;
- *  n = stix_utf8toucs (bcs, &bcslen, ucs, &ucslen);
+ *  n = stix_convutf8touchars (bcs, &bcslen, ucs, &ucslen);
  *  if (n <= -1) { invalid/incomplenete sequence or buffer to small }
  * \endcode
- *
- * For a null-terminated string, you can specify ~(stix_oow_t)0 in
- * \a bcslen. The destination buffer \a ucs also must be large enough to
- * store a terminating null. Otherwise, -2 is returned.
  * 
  * The resulting \a ucslen can still be greater than 0 even if the return
  * value is negative. The value indiates the number of characters converted
@@ -253,7 +249,7 @@ STIX_EXPORT int stix_ucstoutf8 (
  *         -2 if the wide-character string buffer is too small.
  *         -3 if \a bcs is not a complete sequence.
  */
-STIX_EXPORT int stix_utf8toucs (
+STIX_EXPORT int stix_convutf8touchars (
 	const stix_bch_t*   bcs,
 	stix_oow_t*         bcslen,
 	stix_uch_t*         ucs,
@@ -261,6 +257,20 @@ STIX_EXPORT int stix_utf8toucs (
 );
 
 
+STIX_EXPORT int stix_convutoutf8cstr (
+	const stix_uch_t*    ucs,
+	stix_oow_t*          ucslen,
+	stix_bch_t*          bcs,
+	stix_oow_t*          bcslen
+);
+
+STIX_EXPORT int stix_convutf8toucstr (
+	const stix_bch_t*   bcs,
+	stix_oow_t*         bcslen,
+	stix_uch_t*         ucs,
+	stix_oow_t*         ucslen
+);
+
 /* ========================================================================= */
 /* utf8.c                                                                    */
 /* ========================================================================= */
diff --git a/stix/lib/stix.c b/stix/lib/stix.c
index b24a417..75a58f8 100644
--- a/stix/lib/stix.c
+++ b/stix/lib/stix.c
@@ -226,6 +226,11 @@ void stix_seterrnum (stix_t* stix, stix_errnum_t errnum)
 	stix->errnum = errnum;
 }
 
+const stix_ooch_t* stix_geterrstr (stix_t* stix)
+{
+	return stix_errnumtoerrstr (stix->errnum);
+}
+
 int stix_setoption (stix_t* stix, stix_option_t id, const void* value)
 {
 	switch (id)
@@ -390,7 +395,9 @@ stix_mod_data_t* stix_openmod (stix_t* stix, const stix_ooch_t* name, stix_oow_t
 	 */
 	stix_ooch_t buf[MOD_PREFIX_LEN + STIX_MOD_NAME_LEN_MAX + 1 + 1]; 
 
-	/* the terminating null isn't needed in buf here */
+	/* copy instead of encoding conversion. MOD_PREFIX must not
+	 * include a character that requires encoding conversion.
+	 * note the terminating null isn't needed in buf here. */
 	stix_copybctooochars (buf, MOD_PREFIX, MOD_PREFIX_LEN); 
 
 	if (namelen > STIX_COUNTOF(buf) - (MOD_PREFIX_LEN + 1 + 1))
@@ -744,67 +751,3 @@ oops:
 	stix_poptmps (stix, tmp_count);
 	return -1;
 }
- 
-/* -------------------------------------------------------------------------- 
- * SYSTEM DEPENDENT FUNCTIONS - TODO: MOVE THESE ELSE WHERE..........
- * -------------------------------------------------------------------------- */
-#include <errno.h>
-#include <unistd.h>
-#include <signal.h>
-
-stix_errnum_t stix_syserrtoerrnum (int e)
-{
-	switch (e)
-	{
-		case ENOMEM: return STIX_ESYSMEM;
-		case EINVAL: return STIX_EINVAL;
-		case EBUSY: return STIX_EBUSY;
-		case EACCES: return STIX_EACCES;
-		case EPERM: return STIX_EPERM;
-		case ENOTDIR: return STIX_ENOTDIR;
-		case ENOENT: return STIX_ENOENT;
-		case EEXIST: return STIX_EEXIST;
-		case EINTR:  return STIX_EINTR;
-		case EPIPE:  return STIX_EPIPE;
-	#if defined(EAGAIN) && defined(EWOULDBLOCK) && (EAGAIN != EWOULDBLOCK)
-		case EAGAIN: 
-		case EWOULDBLOCK: return STIX_EAGAIN;
-	#elif defined(EAGAIN)
-		case EAGAIN: return STIX_EAGAIN;
-	#elif defined(EWOULDBLOCK)
-		case EWOULDBLOCK: return STIX_EAGAIN;
-	#endif
-		default:     return STIX_ESYSERR;
-	}
-}
-
-void stix_assertfailed (stix_t* stix, const stix_bch_t* expr, const stix_bch_t* file, stix_oow_t line)
-{
-	stix_logbfmt (stix, STIX_LOG_DEBUG, "ASSERTION FAILURE: %s at %s:%zu\n", expr, file, line);
-
-
-#if defined(_WIN32)
-	ExitProcess (249);
-#elif defined(__OS2__)
-	DosExit (EXIT_PROCESS, 249);
-#elif defined(__DOS__)
-	{
-		union REGS regs;
-		regs.h.ah = DOS_EXIT;
-		regs.h.al = 249;
-		intdos (&regs, &regs);
-	}
-#elif defined(vms) || defined(__vms)
-	lib$stop (SS$_ABORT); /* use SS$_OPCCUS instead? */
-
-	/* this won't be reached since lib$stop() terminates the process */
-	sys$exit (SS$_ABORT); /* this condition code can be shown with
-	                       * 'show symbol $status' from the command-line. */
-#elif defined(macintosh)
-	ExitToShell ();
-#else
-	kill (getpid(), SIGABRT);
-	_exit (1);
-#endif
-
-}
diff --git a/stix/lib/stix.h b/stix/lib/stix.h
index 9e65082..dcfa81a 100644
--- a/stix/lib/stix.h
+++ b/stix/lib/stix.h
@@ -44,16 +44,18 @@
  */
 enum stix_errnum_t
 {
-	STIX_ENOERR,  /**< no error */
-	STIX_EOTHER,  /**< other error */
-	STIX_ENOIMPL, /**< not implemented */
-	STIX_ESYSERR, /**< subsystem error */
-	STIX_EINTERN, /**< internal error */
-	STIX_ESYSMEM, /**< insufficient system memory */
-	STIX_EOOMEM,  /**< insufficient object memory */
+	STIX_ENOERR,   /**< no error */
+	STIX_EGENERIC, /**< generic error */
 
-	STIX_EINVAL,  /**< invalid parameter or data */
-	STIX_EEXIST,  /**< existing/duplicate data */
+	STIX_ENOIMPL,  /**< not implemented */
+	STIX_ESYSERR,  /**< subsystem error */
+	STIX_EINTERN,  /**< internal error */
+	STIX_ESYSMEM,  /**< insufficient system memory */
+	STIX_EOOMEM,   /**< insufficient object memory */
+
+	STIX_EINVAL,   /**< invalid parameter or data */
+	STIX_ENOENT,   /**< data not found */
+	STIX_EEXIST,   /**< existing/duplicate data */
 	STIX_EBUSY, 
 	STIX_EACCES,
 	STIX_EPERM,
@@ -62,21 +64,20 @@ enum stix_errnum_t
 	STIX_EPIPE,
 	STIX_EAGAIN,
 
-	STIX_ETOOBIG, /**< data too large */
-	STIX_EMSGSND, /**< message sending error. even doesNotUnderstand: is not found */
-	STIX_ERANGE,  /**< range error. overflow and underflow */
-	STIX_ENOENT,  /**< no matching entry */
-	STIX_EBCFULL, /**< byte-code full */
-	STIX_EDFULL,  /**< dictionary full */
-	STIX_EPFULL,  /**< processor full */
-	STIX_ESHFULL, /**< semaphore heap full */
-	STIX_ESLFULL, /**< semaphore list full */
-	STIX_EDIVBY0, /**< divide by zero */
-	STIX_EIOERR,  /**< I/O error */
-	STIX_EECERR,  /**< encoding conversion error */
+	STIX_ETOOBIG,  /**< data too large */
+	STIX_EMSGSND,  /**< message sending error. even doesNotUnderstand: is not found */
+	STIX_ERANGE,   /**< range error. overflow and underflow */
+	STIX_EBCFULL,  /**< byte-code full */
+	STIX_EDFULL,   /**< dictionary full */
+	STIX_EPFULL,   /**< processor full */
+	STIX_ESHFULL,  /**< semaphore heap full */
+	STIX_ESLFULL,  /**< semaphore list full */
+	STIX_EDIVBY0,  /**< divide by zero */
+	STIX_EIOERR,   /**< I/O error */
+	STIX_EECERR,   /**< encoding conversion error */
 
 #if defined(STIX_INCLUDE_COMPILER)
-	STIX_ESYNTAX /** < syntax error */
+	STIX_ESYNTAX  /** < syntax error */
 #endif
 };
 typedef enum stix_errnum_t stix_errnum_t;
@@ -962,9 +963,11 @@ struct stix_t
 
 /* you can't access arguments and receiver after this macro. 
  * also you must not call this macro more than once */
-#define STIX_STACK_SETRET(stix,nargs,retv) (STIX_STACK_POPS(stix, nargs), STIX_STACK_SETTOP(stix, retv))
+#define STIX_STACK_SETRET(stix,nargs,retv) (STIX_STACK_POPS(stix, nargs), STIX_STACK_SETTOP(stix, (retv)))
 #define STIX_STACK_SETRETTORCV(stix,nargs) (STIX_STACK_POPS(stix, nargs))
-#define STIX_STACK_SETRETTOERROR(stix,nargs,ec) (STIX_STACK_POPS(stix, nargs), STIX_STACK_SETTOP(stix, STIX_ERROR_TO_OOP(ec)))
+#define STIX_STACK_SETRETTOERROR(stix,nargs) STIX_STACK_SETRET(stix, nargs, STIX_ERROR_TO_OOP(stix->errnum))
+/*#define STIX_STACK_SETRETTOERROR(stix,nargs,ec) STIX_STACK_SETRET(stix, nargs, STIX_ERROR_TO_OOP(ec))*/
+
 
 /* =========================================================================
  * STIX VM LOGGING
@@ -1081,6 +1084,10 @@ STIX_EXPORT void stix_seterrnum (
 	stix_errnum_t errnum
 );
 
+STIX_EXPORT const stix_ooch_t* stix_geterrstr (
+	stix_t* stix
+);
+
 /**
  * The stix_getoption() function gets the value of an option
  * specified by \a id into the buffer pointed to by \a value.
@@ -1228,15 +1235,19 @@ STIX_EXPORT int stix_genpfmethod (
  * ========================================================================= */
 
 #if defined(STIX_OOCH_IS_UCH)
-#	define stix_oocstobcs(stix,oocs,oocslen,bcs,bcslen) stix_ucstobcs(stix,oocs,oocslen,bcs,bcslen)
-#	define stix_bcstooocs(stix,bcs,bcslen,oocs,oocslen) stix_bcstoucs(stix,bcs,bcslen,oocs,oocslen)
+#	define stix_convootobchars(stix,oocs,oocslen,bcs,bcslen) stix_convutobchars(stix,oocs,oocslen,bcs,bcslen)
+#	define stix_convbtooochars(stix,bcs,bcslen,oocs,oocslen) stix_convbtouchars(stix,bcs,bcslen,oocs,oocslen)
+#	define stix_convootobcstr(stix,oocs,oocslen,bcs,bcslen) stix_convutobcstr(stix,oocs,oocslen,bcs,bcslen)
+#	define stix_convbtooocstr(stix,bcs,bcslen,oocs,oocslen) stix_convbtoucstr(stix,bcs,bcslen,oocs,oocslen)
 #else
 #error TODO
-#	define stix_oocstobcs(stix,oocs,oocslen,bcs,bcslen) stix_ucstobcs(stix,oocs,oocslen,bcs,bcslen)
-#	define stix_bcstooocs(stix,bcs,bcslen,oocs,oocslen) stix_bcstoucs(stix,bcs,bcslen,oocs,oocslen)
+#	define stix_convootobchars(stix,oocs,oocslen,bcs,bcslen) stix_convutobchars(stix,oocs,oocslen,bcs,bcslen)
+#	define stix_convbtooochars(stix,bcs,bcslen,oocs,oocslen) stix_convbtouchars(stix,bcs,bcslen,oocs,oocslen)
+#	define stix_convootobcstr(stix,oocs,oocslen,bcs,bcslen) stix_convutobcstr(stix,oocs,oocslen,bcs,bcslen)
+#	define stix_convbtooocstr(stix,bcs,bcslen,oocs,oocslen) stix_convbtoucstr(stix,bcs,bcslen,oocs,oocslen)
 #endif
 
-STIX_EXPORT int stix_bcstoucs (
+STIX_EXPORT int stix_convbtouchars (
 	stix_t*           stix,
 	const stix_bch_t* bcs,
 	stix_oow_t*       bcslen,
@@ -1244,7 +1255,7 @@ STIX_EXPORT int stix_bcstoucs (
 	stix_oow_t*       ucslen
 );
 
-STIX_EXPORT int stix_ucstobcs (
+STIX_EXPORT int stix_convutobchars (
 	stix_t*           stix,
 	const stix_uch_t* ucs,
 	stix_oow_t*       ucslen,
@@ -1253,6 +1264,31 @@ STIX_EXPORT int stix_ucstobcs (
 );
 
 
+/**
+ * The stix_convbtoucstr() function converts a null-terminated byte string 
+ * to a wide string.
+ */
+STIX_EXPORT int stix_convbtoucstr (
+	stix_t*           stix,
+	const stix_bch_t* bcs,
+	stix_oow_t*       bcslen,
+	stix_uch_t*       ucs,
+	stix_oow_t*       ucslen
+);
+
+
+/**
+ * The stix_convutobcstr() function converts a null-terminated wide string
+ * to a byte string.
+ */
+int stix_convutobcstr (
+	stix_t*           stix,
+	const stix_uch_t* ucs,
+	stix_oow_t*       ucslen,
+	stix_bch_t*       bcs,
+	stix_oow_t*       bcslen
+);
+
 /* =========================================================================
  * STIX VM LOGGING
  * ========================================================================= */
@@ -1289,9 +1325,12 @@ STIX_EXPORT void stix_assertfailed (
 );
 
 STIX_EXPORT stix_errnum_t stix_syserrtoerrnum (
-	int e
+	int syserr
 );
 
+STIX_EXPORT const stix_ooch_t* stix_errnumtoerrstr (
+	stix_errnum_t errnum
+);
 
 #if defined(__cplusplus)
 }
diff --git a/stix/lib/utl.c b/stix/lib/utl.c
index dba684a..8b04809 100644
--- a/stix/lib/utl.c
+++ b/stix/lib/utl.c
@@ -31,7 +31,10 @@
 /* some naming conventions
  *  bchars, uchars -> pointer and length
  *  bcstr, ucstr -> null-terminated string pointer
- *  bctouchars -> bchars to uchars
+ *  btouchars -> bchars to uchars
+ *  utobchars -> uchars to bchars
+ *  btoucstr -> bcstr to ucstr
+ *  utobcstr -> ucstr to bcstr
  */
 
 stix_oow_t stix_hashbytes (const stix_oob_t* ptr, stix_oow_t len)
@@ -128,8 +131,10 @@ void stix_copybchars (stix_bch_t* dst, const stix_bch_t* src, stix_oow_t len)
 	for (i = 0; i < len; i++) dst[i] = src[i];
 }
 
-void stix_copybctouchars (stix_uch_t* dst, const stix_bch_t* src, stix_oow_t len)
+void stix_copybtouchars (stix_uch_t* dst, const stix_bch_t* src, stix_oow_t len)
 {
+	/* copy without conversions.
+	 * use stix_bctouchars() for conversion encoding */
 	stix_oow_t i;
 	for (i = 0; i < len; i++) dst[i] = src[i];
 }
@@ -572,6 +577,8 @@ static int ucs_to_bcs_with_cmgr (
 	return ret;
 }
 
+/* ----------------------------------------------------------------------- */
+
 static stix_cmgr_t utf8_cmgr =
 {
 	stix_utf8touc,
@@ -583,58 +590,52 @@ stix_cmgr_t* stix_getutf8cmgr (void)
 	return &utf8_cmgr;
 }
 
-int stix_utf8toucs (const stix_bch_t* bcs, stix_oow_t* bcslen, stix_uch_t* ucs, stix_oow_t* ucslen)
+int stix_convutf8touchars (const stix_bch_t* bcs, stix_oow_t* bcslen, stix_uch_t* ucs, stix_oow_t* ucslen)
 {
-	if (*bcslen == ~(stix_oow_t)0)
-	{
-		/* the source is null-terminated. */
-		return bcs_to_ucs_with_cmgr (bcs, bcslen, ucs, ucslen, &utf8_cmgr, 0);
-	}
-	else
-	{
-		/* the source is length bound */
-		return bcsn_to_ucsn_with_cmgr (bcs, bcslen, ucs, ucslen, &utf8_cmgr, 0);
-	}
+	/* the source is length bound */
+	return bcsn_to_ucsn_with_cmgr (bcs, bcslen, ucs, ucslen, &utf8_cmgr, 0);
 }
 
-int stix_ucstoutf8 (const stix_uch_t* ucs, stix_oow_t* ucslen, stix_bch_t* bcs, stix_oow_t* bcslen)
+int stix_convutoutf8chars (const stix_uch_t* ucs, stix_oow_t* ucslen, stix_bch_t* bcs, stix_oow_t* bcslen)
 {
-	if (*ucslen == ~(stix_oow_t)0)
-	{
-		/* null-terminated */
-		return ucs_to_bcs_with_cmgr (ucs, ucslen, bcs, bcslen, &utf8_cmgr);
-	}
-	else
-	{
-		/* length bound */
-		return ucsn_to_bcsn_with_cmgr (ucs, ucslen, bcs, bcslen, &utf8_cmgr);
-	}
+	/* length bound */
+	return ucsn_to_bcsn_with_cmgr (ucs, ucslen, bcs, bcslen, &utf8_cmgr);
 }
 
-int stix_bcstoucs (stix_t* stix, const stix_bch_t* bcs, stix_oow_t* bcslen, stix_uch_t* ucs, stix_oow_t* ucslen)
+int stix_convutf8toucstr (const stix_bch_t* bcs, stix_oow_t* bcslen, stix_uch_t* ucs, stix_oow_t* ucslen)
 {
-	if (*bcslen == ~(stix_oow_t)0)
-	{
-		/* the source is null-terminated. */
-		return bcs_to_ucs_with_cmgr (bcs, bcslen, ucs, ucslen, stix->cmgr, 0);
-	}
-	else
-	{
-		/* the source is length bound */
-		return bcsn_to_ucsn_with_cmgr (bcs, bcslen, ucs, ucslen, stix->cmgr, 0);
-	}
+	/* null-terminated. */
+	return bcs_to_ucs_with_cmgr (bcs, bcslen, ucs, ucslen, &utf8_cmgr, 0);
 }
 
-int stix_ucstobcs (stix_t* stix, const stix_uch_t* ucs, stix_oow_t* ucslen, stix_bch_t* bcs, stix_oow_t* bcslen)
+int stix_convutoutf8cstr (const stix_uch_t* ucs, stix_oow_t* ucslen, stix_bch_t* bcs, stix_oow_t* bcslen)
 {
-	if (*ucslen == ~(stix_oow_t)0)
-	{
-		/* null-terminated */
-		return ucs_to_bcs_with_cmgr (ucs, ucslen, bcs, bcslen, stix->cmgr);
-	}
-	else
-	{
-		/* length bound */
-		return ucsn_to_bcsn_with_cmgr (ucs, ucslen, bcs, bcslen, stix->cmgr);
-	}
+	/* null-terminated */
+	return ucs_to_bcs_with_cmgr (ucs, ucslen, bcs, bcslen, &utf8_cmgr);
+}
+
+/* ----------------------------------------------------------------------- */
+
+int stix_convbtouchars (stix_t* stix, const stix_bch_t* bcs, stix_oow_t* bcslen, stix_uch_t* ucs, stix_oow_t* ucslen)
+{
+	/* length bound */
+	return bcsn_to_ucsn_with_cmgr (bcs, bcslen, ucs, ucslen, stix->cmgr, 0);
+}
+
+int stix_convutobchars (stix_t* stix, const stix_uch_t* ucs, stix_oow_t* ucslen, stix_bch_t* bcs, stix_oow_t* bcslen)
+{
+	/* length bound */
+	return ucsn_to_bcsn_with_cmgr (ucs, ucslen, bcs, bcslen, stix->cmgr);
+}
+
+int stix_convbtoucstr (stix_t* stix, const stix_bch_t* bcs, stix_oow_t* bcslen, stix_uch_t* ucs, stix_oow_t* ucslen)
+{
+	/* null-terminated. */
+	return bcs_to_ucs_with_cmgr (bcs, bcslen, ucs, ucslen, stix->cmgr, 0);
+}
+
+int stix_convutobcstr (stix_t* stix, const stix_uch_t* ucs, stix_oow_t* ucslen, stix_bch_t* bcs, stix_oow_t* bcslen)
+{
+	/* null-terminated */
+	return ucs_to_bcs_with_cmgr (ucs, ucslen, bcs, bcslen, stix->cmgr);
 }
diff --git a/stix/mod/console.c b/stix/mod/console.c
index fd427fb..6da3511 100644
--- a/stix/mod/console.c
+++ b/stix/mod/console.c
@@ -166,7 +166,7 @@ static int pf_write (stix_t* stix, stix_ooi_t nargs)
 	{
 		ucslen = ucsrem;
 		bcslen = STIX_COUNTOF(bcs);
-		if ((n = stix_oocstobcs (stix, &oomsg->slot[ucspos], &ucslen, bcs, &bcslen)) <= -1)
+		if ((n = stix_convootobchars (stix, &oomsg->slot[ucspos], &ucslen, bcs, &bcslen)) <= -1)
 		{
 			if (n != -2 || ucslen <= 0) 
 			{
diff --git a/stix/mod/stdio.c b/stix/mod/stdio.c
index 99f27b4..9d537df 100644
--- a/stix/mod/stdio.c
+++ b/stix/mod/stdio.c
@@ -63,15 +63,14 @@ static int pf_open (stix_t* stix, stix_ooi_t nargs)
 	mode = (stix_oop_char_t)STIX_STACK_GETARG(stix, nargs, 1);
 
 #if defined(STIX_OOCH_IS_UCH)
-/* TODO: error check on string conversion */
 	ucslen = STIX_OBJ_GET_SIZE(name);
 	bcslen = STIX_COUNTOF(namebuf) - 1;
-	stix_oocstobcs (stix, name->slot, &ucslen, namebuf, &bcslen); /* TODO: error check */
+	if (stix_convootobchars (stix, name->slot, &ucslen, namebuf, &bcslen) <= -1) goto reterr;
 	namebuf[bcslen] = '\0';
 
 	ucslen = STIX_OBJ_GET_SIZE(mode);
 	bcslen = STIX_COUNTOF(modebuf) - 1;
-	stix_oocstobcs (stix, mode->slot, &ucslen, modebuf, &bcslen); /* TODO: error check */
+	if (stix_convootobchars (stix, mode->slot, &ucslen, modebuf, &bcslen) <= -1) goto reterr;
 	modebuf[bcslen] = '\0';
 
 	rcv->fp = fopen (namebuf, modebuf);
@@ -81,13 +80,17 @@ static int pf_open (stix_t* stix, stix_ooi_t nargs)
 	if (!rcv->fp) 
 	{
 STIX_DEBUG2 (stix, "cannot open %s for %s\n", namebuf, modebuf);
-		STIX_STACK_SETRETTOERROR (stix, nargs, stix_syserrtoerrnum(errno));
-		return 1;
+		stix_seterrnum (stix, stix_syserrtoerrnum(errno));
+		goto reterr;
 	}
 
 STIX_DEBUG3 (stix, "opened %s for %s - %p\n", namebuf, modebuf, rcv->fp);
 	STIX_STACK_SETRETTORCV (stix, nargs);
 	return 1;
+
+reterr:
+	STIX_STACK_SETRETTOERROR (stix, nargs);
+	return 1;
 }
 
 static int pf_close (stix_t* stix, stix_ooi_t nargs)
@@ -113,7 +116,7 @@ static int pf_gets (stix_t* stix, stix_ooi_t nargs)
 	return 1;
 }
 
-static int pf_puts (stix_t* stix, stix_ooi_t nargs)
+static int __pf_puts (stix_t* stix, stix_ooi_t nargs, stix_oow_t limit)
 {
 	stdio_t* rcv;
 	stix_ooi_t i;
@@ -145,31 +148,29 @@ static int pf_puts (stix_t* stix, stix_ooi_t nargs)
 		puts_string:
 			ucspos = 0;
 			ucsrem = STIX_OBJ_GET_SIZE(x);
+			if (ucsrem > limit) ucsrem = limit;
+
 			while (ucsrem > 0)
 			{
 				ucslen = ucsrem;
 				bcslen = STIX_COUNTOF(bcs);
-/* TODO: implement character conversion into stdio and use it */
-				if ((n = stix_oocstobcs (stix, &x->slot[ucspos], &ucslen, bcs, &bcslen)) <= -1)
+
+/* TODO: implement character conversion into stdio and use it instead of vm's conversion facility. */
+				if ((n = stix_convootobchars (stix, &x->slot[ucspos], &ucslen, bcs, &bcslen)) <= -1)
 				{
 					if (n != -2 || ucslen <= 0) 
 					{
-/* TODO: 
- * 
-STIX_STACK_SETRET (stix, nargs, stix->_error);
-return 1;
- * 
- */
 						stix_seterrnum (stix, STIX_EECERR);
-						return -1;
+						goto reterr;
 					}
 				}
 
-				fwrite (bcs, bcslen, 1, rcv->fp); 
-/* TODO; error handling...
-STIX_STACK_SETRET (stix, nargs, stix->_error);
-return 1;
-*/
+				if (fwrite (bcs, 1, bcslen, rcv->fp) < bcslen)
+				{
+					stix_seterrnum (stix, stix_syserrtoerrnum(errno));
+					goto reterr;
+				}
+
 		/* TODO: abort looping for async processing???? */
 				ucspos += ucslen;
 				ucsrem -= ucslen;
@@ -177,21 +178,30 @@ return 1;
 		}
 		else
 		{
-/* TODO;
-STIX_STACK_SETRET (stix, nargs, stix->_error);
-return 1;
-*/
-STIX_DEBUG1 (stix, "ARGUMETN ISN INVALID...[%O]\n", x);
 			stix_seterrnum (stix, STIX_EINVAL);
-			return -1;
+			goto reterr;
 		}
 	}
 
 	STIX_STACK_SETRETTORCV (stix, nargs);
 	return 1;
+
+reterr:
+	STIX_STACK_SETRETTOERROR (stix, nargs);
+	return 1;
 }
 
 
+static int pf_putc (stix_t* stix, stix_ooi_t nargs)
+{
+	return __pf_puts (stix, nargs, 1);
+}
+
+static int pf_puts (stix_t* stix, stix_ooi_t nargs)
+{
+	return __pf_puts (stix, nargs, STIX_TYPE_MAX(stix_oow_t));
+}
+
 /* ------------------------------------------------------------------------ */
 
 typedef struct fnctab_t fnctab_t;
@@ -212,6 +222,8 @@ static fnctab_t fnctab[] =
 	{ I, { 'c','l','o','s','e','\0' },                             0, pf_close         },
 	{ I, { 'g','e','t','s','\0' },                                 0, pf_gets          },
 	{ I, { 'o','p','e','n',':','f','o','r',':','\0' },             0, pf_open          },
+	{ I, { 'p','u','t','c','\0' },                                 1, pf_putc          },
+	{ I, { 'p','u','t','c',':','\0' },                             0, pf_putc          },
 	{ I, { 'p','u','t','s','\0' },                                 1, pf_puts          },
 	{ I, { 'p','u','t','s',':','\0' },                             0, pf_puts          }
 };