diff --git a/moo/lib/fmtoutv.h b/moo/lib/fmtoutv.h
index f34dfbc..cd84060 100644
--- a/moo/lib/fmtoutv.h
+++ b/moo/lib/fmtoutv.h
@@ -89,6 +89,9 @@
 	} \
 } while (0)
 
+/* TODO: redefine this */
+#define BYTE_PRINTABLE(x) ((x >= 'a' && x <= 'z') || (x >= 'A' &&  x <= 'Z'))
+
 static int fmtoutv (moo_t* moo, const fmtchar_t* fmt, moo_fmtout_data_t* data, va_list ap, moo_outbfmt_t outbfmt)
 {
 	const fmtchar_t* percent;
@@ -598,6 +601,87 @@ static int fmtoutv (moo_t* moo, const fmtchar_t* fmt, moo_fmtout_data_t* data, v
 			break;
 		}
 
+		case 'k':
+		case 'K':
+		{
+			const moo_uint8_t* bsp;
+			moo_oow_t bslen, slen, k_hex_width;
+
+			/* zeropad must not take effect for 'k' and 'K' 
+			 * 
+ 			 * 'h' & 'l' is not used to differentiate qse_mchar_t and qse_wchar_t
+			 * because 'k' means qse_byte_t. 
+			 * 'l', results in uppercase hexadecimal letters. 
+			 * 'h' drops the leading \x in the output 
+			 * --------------------------------------------------------
+			 * hk -> \x + non-printable in lowercase hex
+			 * k -> all in lowercase hex
+			 * lk -> \x +  all in lowercase hex
+			 * --------------------------------------------------------
+			 * hK -> \x + non-printable in uppercase hex
+			 * K -> all in uppercase hex
+			 * lK -> \x +  all in uppercase hex
+			 * --------------------------------------------------------
+			 * with 'k' or 'K', i don't substitute "(null)" for the NULL pointer
+			 */
+			if (flagc & FLAGC_ZEROPAD) padc = ' ';
+
+			bsp = va_arg(ap, moo_uint8_t*);
+			k_hex_width = (lm_flag & (LF_H | LF_L))? 4: 2;
+
+			if (lm_flag& LF_H)
+			{
+				if (flagc & FLAGC_DOT)
+				{
+					/* if precision is specifed, it doesn't stop at the value of zero unlike 's' or 'S' */
+					for (n = 0; n < precision; n++) width -= BYTE_PRINTABLE(bsp[n])? 1: k_hex_width;
+				}
+				else
+				{
+					for (n = 0; bsp[n]; n++) width -= BYTE_PRINTABLE(bsp[n])? 1: k_hex_width;
+				}
+			}
+			else
+			{
+				if (flagc & FLAGC_DOT)
+				{
+					/* if precision is specifed, it doesn't stop at the value of zero unlike 's' or 'S' */
+					for (n = 0; n < precision; n++) /* nothing */;
+				}
+				else
+				{
+					for (n = 0; bsp[n]; n++) /* nothing */;
+				}
+				width -= (n * k_hex_width);
+			}
+
+			if (!(flagc & FLAGC_LEFTADJ) && width > 0) PUT_OOCH (padc, width);
+
+			while (n--) 
+			{
+				if ((lm_flag & LF_H) && BYTE_PRINTABLE(*bsp)) 
+				{
+					PUT_OOCH(*bsp, 1);
+				}
+				else
+				{
+					moo_bch_t xbuf[3];
+					moo_byte_to_bcstr (*bsp, xbuf, MOO_COUNTOF(xbuf), (16 | (ch == 'k'? MOO_BYTE_TO_BCSTR_LOWERCASE: 0)), '0');
+					if (lm_flag & (LF_H | LF_L))
+					{
+						PUT_OOCH('\\', 1);
+						PUT_OOCH('x', 1);
+					}
+					PUT_OOCH(xbuf[0], 1);
+					PUT_OOCH(xbuf[1], 1);
+				}
+				bsp++;
+			}
+
+			if ((flagc & FLAGC_LEFTADJ) && width > 0) PUT_OOCH (padc, width);
+			break;
+		}
+
 		case 'O': /* object - ignore precision, width, adjustment */
 			if (print_object(moo, data->mask, va_arg(ap, moo_oop_t), outbfmt) <= -1) goto oops;
 			break;
diff --git a/moo/lib/moo-utl.h b/moo/lib/moo-utl.h
index 05fc826..ad20243 100644
--- a/moo/lib/moo-utl.h
+++ b/moo/lib/moo-utl.h
@@ -428,6 +428,19 @@ MOO_EXPORT moo_oow_t moo_count_bcstr (
 
 /* ------------------------------------------------------------------------- */
 
+#define MOO_BYTE_TO_BCSTR_RADIXMASK (0xFF)
+#define MOO_BYTE_TO_BCSTR_LOWERCASE (1 << 8)
+
+moo_oow_t moo_byte_to_bcstr (
+	moo_uint8_t   byte,  
+	moo_bch_t*    buf,
+	moo_oow_t     size,
+	int           flagged_radix,
+	moo_bch_t     fill
+);
+
+/* ------------------------------------------------------------------------- */
+
 MOO_EXPORT int moo_ucwidth (
 	moo_uch_t uc
 );
diff --git a/moo/lib/utl.c b/moo/lib/utl.c
index 35c07ae..20d0f49 100644
--- a/moo/lib/utl.c
+++ b/moo/lib/utl.c
@@ -541,6 +541,42 @@ moo_bch_t* moo_find_bchar_in_bcstr (const moo_bch_t* ptr, moo_bch_t c)
 
 /* ----------------------------------------------------------------------- */
 
+moo_oow_t moo_byte_to_bcstr (moo_uint8_t byte, moo_bch_t* buf, moo_oow_t size, int flagged_radix, moo_bch_t fill)
+{
+	moo_bch_t tmp[(MOO_SIZEOF(moo_uint8_t) * 8)];
+	moo_bch_t* p = tmp, * bp = buf, * be = buf + size - 1;
+	int radix;
+	moo_bch_t radix_char;
+
+	radix = (flagged_radix & MOO_BYTE_TO_BCSTR_RADIXMASK);
+	radix_char = (flagged_radix & MOO_BYTE_TO_BCSTR_LOWERCASE)? 'a': 'A';
+	if (radix < 2 || radix > 36 || size <= 0) return 0;
+
+	do 
+	{
+		moo_uint8_t digit = byte % radix;	
+		if (digit < 10) *p++ = digit + '0';
+		else *p++ = digit + radix_char - 10;
+		byte /= radix;
+	}
+	while (byte > 0);
+
+	if (fill != '\0') 
+	{
+		while (size - 1 > p - tmp) 
+		{
+			*bp++ = fill;
+			size--;
+		}
+	}
+
+	while (p > tmp && bp < be) *bp++ = *--p;
+	*bp = '\0';
+	return bp - buf;
+}
+
+/* ----------------------------------------------------------------------- */
+
 MOO_INLINE int moo_conv_bchars_to_uchars_with_cmgr (
 	const moo_bch_t* bcs, moo_oow_t* bcslen,
 	moo_uch_t* ucs, moo_oow_t* ucslen, moo_cmgr_t* cmgr, int all)