diff --git a/Makefile b/Makefile
index ea8521b..ab9e689 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 CXXSTD :=	c++14
-CXXFLAGS :=	-std=$(CXXSTD) -Wall -Werror -O0 -g -static
+CXXFLAGS :=	-std=$(CXXSTD) -Wall -Werror -O0 -g
 LDFLAGS :=	-static
 OBJS :=		linux/io.o	\
 		io.o		\
@@ -13,7 +13,7 @@ TARGET :=	kforth
 all: $(TARGET)
 
 $(TARGET): $(OBJS)
-	$(CXX) $(CXXFLAGS) -o $@ $(OBJS)
+	$(CXX) $(LDFLAGS) -o $@ $(OBJS)
 
 clean:
 	rm -f $(OBJS) $(TARGET)
diff --git a/TODO.txt b/TODO.txt
index fa5e2de..cf70a30 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -1,20 +1,8 @@
 nucleus layer:
-+ !
-+ +!
-+ @
-+ C!
-+ C@
-+ CMOVE
-+ CMOVE>
-+ COUNT
-+ FILL
-+ EXECUTE
-+ EXIT
-+ I
-+ J
-+ >R
-+ R>
-+ R@
-+ U<
-+ UM*
-+ UM/MOD
++ EXIT: requires better execution control
++ I: requires support for loop index
++ J: requires support for loop index
+
+return addressing / rstack
+dictionary -> fixed size stack / array
+
diff --git a/dict.cc b/dict.cc
index baf7e21..90a798e 100644
--- a/dict.cc
+++ b/dict.cc
@@ -7,8 +7,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-constexpr size_t dshift = (sizeof(KF_INT) * 8) - 1;
-
 static bool
 pop_long(System *sys, KF_LONG *d)
 {
@@ -30,18 +28,6 @@ pop_long(System *sys, KF_LONG *d)
 	return true;
 }
 
-static inline KF_INT
-mask(size_t bits)
-{
-	KF_INT m = 0;
-
-	for (size_t i = 0; i < bits; i++) {
-		m += 1 << i;
-	}
-	
-	return m;
-}
-
 static bool
 push_long(System *sys, KF_LONG d)
 {
@@ -62,6 +48,33 @@ push_long(System *sys, KF_LONG d)
 	return true;
 }
 
+static bool
+pop_addr(System *sys, KF_ADDR *a)
+{
+	KF_LONG	b;
+	if (!pop_long(sys, &b)) {
+		// Status is already set.
+		return false;
+	}
+
+	*a = static_cast<KF_ADDR>(b);
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+push_addr(System *sys, KF_ADDR a)
+{
+	KF_LONG	b = static_cast<KF_LONG>(a);
+	if (!push_long(sys, b)) {
+		// Status is already set.
+		return false;
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
 static bool
 add(System *sys)
 {
@@ -468,27 +481,25 @@ divide_mod(System *sys)
 	return true;
 }
 
-
-/*
 static bool
 store(System *sys)
 {
-	KF_INT	a = 0; // address
+	KF_ADDR	a = 0; // address
 	KF_INT	b = 0; // value
+	KF_LONG	c = 0; // temporary
 
-	if (!sys->dstack.pop(&a)) {
+	if (!pop_long(sys, &c)) {
 		sys->status = STATUS_STACK_UNDERFLOW;
 		return false;
 	}
+	a = static_cast<KF_ADDR>(c);
 	
 	if (!sys->dstack.pop(&b)) {
 		sys->status = STATUS_STACK_UNDERFLOW;
 		return false;
 	}
 
-	KF_INT	*p = (KF_INT *)(a);
-	*p = b;
-	
+	*((KF_INT *)a) = b;
 	sys->status = STATUS_OK;
 	return true;
 }
@@ -496,26 +507,47 @@ store(System *sys)
 static bool
 plus_store(System *sys)
 {
-	KF_INT	a = 0; // address
+	KF_ADDR	a = 0; // address
 	KF_INT	b = 0; // value
+	KF_LONG	c = 0; // temporary
 
-	if (!sys->dstack.pop(&a)) {
+	if (!pop_long(sys, &c)) {
 		sys->status = STATUS_STACK_UNDERFLOW;
 		return false;
 	}
+	a = static_cast<KF_ADDR>(c);
 	
 	if (!sys->dstack.pop(&b)) {
 		sys->status = STATUS_STACK_UNDERFLOW;
 		return false;
 	}
 
-	KF_INT	*p = (KF_INT *)(a);
-	*p += b;
-	
+	*((KF_INT *)a) += b;
 	sys->status = STATUS_OK;
 	return true;
 }
-*/
+
+static bool
+fetch(System *sys)
+{
+	KF_ADDR	a = 0; // address
+	KF_INT	b = 0; // value
+	KF_LONG	c = 0; // temporary
+
+	if (!pop_long(sys, &c)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	a = static_cast<KF_ADDR>(c);
+	
+	b = *((KF_INT *)a);
+	if (!sys->dstack.push(b)) {
+		sys->status = STATUS_STACK_OVERFLOW;
+		return false;
+	}
+	sys->status = STATUS_OK;
+	return true;	
+}
 
 static bool
 zero_less(System *sys)
@@ -1173,14 +1205,379 @@ mod(System *sys)
 	return true;
 }
 
+static bool
+to_r(System *sys)
+{
+	KF_INT	a;
+
+	if (!sys->dstack.pop(&a)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+
+	if (!sys->rstack.push(static_cast<KF_ADDR>(a))) {
+		sys->status = STATUS_RSTACK_OVERFLOW;
+		return false;
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+from_r(System *sys)
+{
+	KF_ADDR	a;
+
+	if (!sys->rstack.pop(&a)) {
+		sys->status = STATUS_RSTACK_UNDERFLOW;
+		return false;
+	}
+
+	if (!sys->dstack.push(static_cast<KF_INT>(a))) {
+		sys->status = STATUS_STACK_OVERFLOW;
+		return false;
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+r_fetch(System *sys)
+{
+	KF_ADDR	a;
+
+	if (!sys->rstack.peek(&a)) {
+		sys->status = STATUS_RSTACK_UNDERFLOW;
+		return false;
+	}
+
+	if (!sys->dstack.push(static_cast<KF_INT>(a))) {
+		sys->status = STATUS_STACK_OVERFLOW;
+		return false;
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+c_fetch(System *sys)
+{
+	KF_ADDR	a;
+	uint8_t	b; // the standard explicitly calls for a byte.
+
+	if (!pop_addr(sys, &a)) {
+		// Status is already set.
+		return false;
+	}
+
+	b = *(reinterpret_cast<uint8_t *>(a));
+	if (!sys->dstack.push(static_cast<KF_INT>(b))) {
+		sys->status = STATUS_STACK_OVERFLOW;
+		return false;
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+c_store(System *sys)
+{
+	KF_ADDR	a;
+	KF_INT	b;
+
+	if (!pop_addr(sys, &a)) {
+		// Status is already set.
+		return false;
+	}
+
+	if (!sys->dstack.pop(&b)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+
+	b &= 0xFF;
+
+	*(reinterpret_cast<uint8_t *>(a)) = b;
+	sys->status = STATUS_OK;
+	return true;
+}
+
+
+static bool
+c_move(System *sys)
+{
+	KF_UINT	a;
+	KF_INT	b;
+	KF_ADDR	c, d;
+
+	if (!sys->dstack.pop(&b)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	a = static_cast<KF_UINT>(b);
+
+	if (!pop_addr(sys, &d)) {
+		// Status is already set.
+		return false;
+	}
+
+	if (!pop_addr(sys, &c)) {
+		// Status is already set.
+		return false;
+	}
+
+	for (KF_UINT i = 0; i < a; i++) {
+		*reinterpret_cast<uint8_t *>(d + i) = 
+		*reinterpret_cast<uint8_t *>(c + i);
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+c_move_up(System *sys)
+{
+	KF_UINT	a;
+	KF_INT	b;
+	KF_ADDR	c, d;
+
+	if (!sys->dstack.pop(&b)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	a = static_cast<KF_UINT>(b);
+
+	if (!pop_addr(sys, &d)) {
+		// Status is already set.
+		return false;
+	}
+
+	if (!pop_addr(sys, &c)) {
+		// Status is already set.
+		return false;
+	}
+
+	for (KF_UINT i = 0; i < a; i++) {
+		*reinterpret_cast<uint8_t *>(d - i) = 
+		*reinterpret_cast<uint8_t *>(c - i);
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+fill(System *sys)
+{
+	KF_INT	a, c;
+	uint8_t	b;
+	KF_UINT d;
+	KF_ADDR	e;
+
+	if (!sys->dstack.pop(&a)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	b = static_cast<uint8_t>(a);
+
+	if (!sys->dstack.pop(&c)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	d = static_cast<KF_UINT>(c);
+
+	if (!pop_addr(sys, &e)) {
+		// Status is already set.
+		return false;
+	}
+
+	for (KF_UINT i = 0; i < d; i++) {
+		*reinterpret_cast<uint8_t *>(e + i) = b;
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+count(System *sys)
+{
+	uint8_t	a;
+	KF_ADDR	b;
+
+	if (!pop_addr(sys, &b)) {
+		// Status is already set.
+		return false;
+	}
+
+	a = *reinterpret_cast<uint8_t *>(b);
+	b++;
+
+	if (!push_addr(sys, b)) {
+		// Status is already set.
+		return false;
+	}
+
+	if (!sys->dstack.push(static_cast<KF_INT>(a))) {
+		sys->status = STATUS_STACK_OVERFLOW;
+		return false;
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+execute(System *sys)
+{
+	KF_ADDR	 a;
+	Word	*b;
+
+	if (!pop_addr(sys, &a)) {
+		// Status is already set.
+		return false;
+	}
+
+	b = reinterpret_cast<Word *>(a);
+	char	buf[MAX_TOKEN_LENGTH];
+	size_t	buflen;
+
+	b->getname(buf, &buflen);
+	sys->interface->wrbuf((char *)"executing word: ", 16);
+	sys->interface->wrbuf(buf, buflen);
+	sys->interface->newline();
+	return b->eval(sys);
+}
+
+static bool
+u_dot(System *sys)
+{
+	KF_INT	a;
+	KF_UINT	b;
+
+	if (!sys->dstack.pop(&a)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	b = static_cast<KF_UINT>(a);
+
+	write_unum(sys->interface, b);
+	sys->interface->newline();
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+ult(System *sys)
+{
+	KF_INT	a, b;
+	bool	ok;
+
+	if (!sys->dstack.pop(&a)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	
+	if (!sys->dstack.pop(&b)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	
+	if (static_cast<KF_UINT>(b) < static_cast<KF_UINT>(a)) {
+		ok = sys->dstack.push(-1);
+	}
+	else {
+		ok = sys->dstack.push(0);
+	}
+
+	if (!ok) {
+		sys->status = STATUS_STACK_OVERFLOW;
+		return false;
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+u_times(System *sys)
+{
+	KF_INT	a, b;
+
+	if (!sys->dstack.pop(&a)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	
+	if (!sys->dstack.pop(&b)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	
+	a = static_cast<KF_UINT>(a) * static_cast<KF_UINT>(b);
+	if (!sys->dstack.push(a)) {
+		sys->status = STATUS_STACK_OVERFLOW;
+		return false;
+	}
+
+	sys->status = STATUS_OK;
+	return true;
+}
+
+static bool
+udivide_mod(System *sys)
+{
+	KF_INT	a, b;
+	KF_INT	y, z;
+	
+	if (!sys->dstack.pop(&a)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	
+	if (!sys->dstack.pop(&b)) {
+		sys->status = STATUS_STACK_UNDERFLOW;
+		return false;
+	}
+	
+	
+	z = (KF_UINT)b / (KF_UINT)a;
+	y = (KF_UINT)b % (KF_UINT)a;
+
+	if (!sys->dstack.push(y)) {
+		sys->status = STATUS_STACK_OVERFLOW;
+		return false;
+	}
+	
+	if (!sys->dstack.push(z)) {
+		sys->status = STATUS_STACK_OVERFLOW;
+		return false;
+	}
+	
+	sys->status = STATUS_OK;
+	return true;
+}
+
 void
 init_dict(System *sys)
 {
 	sys->dict = nullptr;
+	sys->dict = new Builtin((const char *)"U/MOD", 5, sys->dict, udivide_mod);
+	sys->dict = new Builtin((const char *)"UM*", 3, sys->dict, u_times);
+	sys->dict = new Builtin((const char *)"U<", 2, sys->dict, ult);
+	sys->dict = new Builtin((const char *)"U.", 2, sys->dict, u_dot);
+	sys->dict = new Builtin((const char *)"SWAP", 4, sys->dict, swap);
 	sys->dict = new Builtin((const char *)"SWAP", 4, sys->dict, swap);
 	sys->dict = new Builtin((const char *)"XOR", 3, sys->dict, exclusive_or);
 	sys->dict = new Builtin((const char *)"ROT", 3, sys->dict, rot);
 	sys->dict = new Builtin((const char *)"ROLL", 4, sys->dict, roll);
+	sys->dict = new Builtin((const char *)"R@", 2, sys->dict, r_fetch);
+	sys->dict = new Builtin((const char *)"R>", 2, sys->dict, from_r);
 	sys->dict = new Builtin((const char *)"PICK", 4, sys->dict, pick);
 	sys->dict = new Builtin((const char *)"OVER", 4, sys->dict, over);
 	sys->dict = new Builtin((const char *)"NEGATE", 6, sys->dict, negate);
@@ -1188,6 +1585,8 @@ init_dict(System *sys)
 	sys->dict = new Builtin((const char *)"MOD", 3, sys->dict, mod);
 	sys->dict = new Builtin((const char *)"MIN", 3, sys->dict, min);
 	sys->dict = new Builtin((const char *)"MAX", 3, sys->dict, max);
+	sys->dict = new Builtin((const char *)"FILL", 4, sys->dict, fill);
+	sys->dict = new Builtin((const char *)"EXECUTE", 7, sys->dict, execute);
 	sys->dict = new Builtin((const char *)"DUP", 3, sys->dict, dup);
 	sys->dict = new Builtin((const char *)"DROP", 4, sys->dict, drop);
 	sys->dict = new Builtin((const char *)"DEPTH", 5, sys->dict, depth);
@@ -1196,10 +1595,17 @@ init_dict(System *sys)
 	sys->dict = new Builtin((const char *)"D.", 2, sys->dict, ddot);
 	sys->dict = new Builtin((const char *)"D<", 2, sys->dict, dlt);
 	sys->dict = new Builtin((const char *)"D+", 2, sys->dict, dplus);
+	sys->dict = new Builtin((const char *)"COUNT", 5, sys->dict, count);
+	sys->dict = new Builtin((const char *)"CMOVE>", 6, sys->dict, c_move_up);
+	sys->dict = new Builtin((const char *)"CMOVE", 5, sys->dict, c_move);
+	sys->dict = new Builtin((const char *)"C@", 2, sys->dict, c_fetch);
+	sys->dict = new Builtin((const char *)"C!", 2, sys->dict, c_store);
 	sys->dict = new Builtin((const char *)"BYE", 3, sys->dict, bye);
 	sys->dict = new Builtin((const char *)"ABS", 3, sys->dict, absolute);
 	sys->dict = new Builtin((const char *)"AND", 3, sys->dict, land);
+	sys->dict = new Builtin((const char *)"@", 1, sys->dict, fetch);
 	sys->dict = new Builtin((const char *)"?DUP", 4, sys->dict, question_dupe);
+	sys->dict = new Builtin((const char *)">R", 2, sys->dict, to_r);
 	sys->dict = new Builtin((const char *)">", 1, sys->dict, greater_than);
 	sys->dict = new Builtin((const char *)"=", 1, sys->dict, equals);
 	sys->dict = new Builtin((const char *)"<", 1, sys->dict, less_than);
@@ -1218,10 +1624,12 @@ init_dict(System *sys)
 	sys->dict = new Builtin((const char *)".S", 2, sys->dict, dotess);
 	sys->dict = new Builtin((const char *)".", 1, sys->dict, dot);
 	sys->dict = new Builtin((const char *)"-", 1, sys->dict, sub);
-	// sys->dict = new Builtin((const char *)"+!", 2, sys->dict, plus_store);
+	sys->dict = new Builtin((const char *)"+!", 2, sys->dict, plus_store);
 	sys->dict = new Builtin((const char *)"+", 1, sys->dict, add);
 	sys->dict = new Builtin((const char *)"*", 1, sys->dict, mul);
-	// sys->dict = new Builtin((const char *)"!", 1, sys->dict, store);
+	sys->dict = new Builtin((const char *)"!", 1, sys->dict, store);
+	sys->dict = new Address((const char *)"ARENA", 5, sys->dict, reinterpret_cast<KF_ADDR>(&sys->arena));
+	sys->dict = new Address((const char *)"DICT", 5, sys->dict, reinterpret_cast<KF_ADDR>(&sys->dict));
 }
 
 bool
diff --git a/doc/part-0x01.rst b/doc/part-0x01.rst
index eb5feb4..72fecf4 100644
--- a/doc/part-0x01.rst
+++ b/doc/part-0x01.rst
@@ -9,6 +9,12 @@ X-type series where I'll write up my thinking and planning as I go.
 
 .. _last post: https://dl.kyleisom.net/posts/2018/02/21/2018-02-21-revisiting-forth/
 
+I've always wanted to write a Forth_; I've made a few attempts_ at it in the
+past. This time, I'm actually going to do it.
+
+.. _Forth: https://en.wikipedia.org/wiki/Forth_(programming_language)
+.. _attempts: https://github.com/isrlabs/avr-forth
+
 The basics
 ^^^^^^^^^^
 
diff --git a/io.cc b/io.cc
index f2521c8..a04dc6f 100644
--- a/io.cc
+++ b/io.cc
@@ -30,6 +30,29 @@ write_num(IO *interface, KF_INT n)
 	interface->wrbuf(buf+i, nbuflen - i);
 }
 
+void
+write_unum(IO *interface, KF_UINT n)
+{
+	static constexpr size_t	nbuflen = 11;
+	char buf[nbuflen];
+	uint8_t i = nbuflen - 1;
+	memset(buf, 0, nbuflen);
+
+	if (n == 0) {
+		interface->wrch('0');
+		return;
+	}
+
+	while (n != 0) {
+		char x = n % 10;
+		x += '0';
+		buf[i--] = x;
+		n /= 10;
+	}
+
+	interface->wrbuf(buf+i, nbuflen - i);
+}
+
 void
 write_dnum(IO *interface, KF_LONG n)
 {
diff --git a/io.h b/io.h
index 6e876a6..d5a75c1 100644
--- a/io.h
+++ b/io.h
@@ -25,6 +25,7 @@ public:
 };
 
 void	write_num(IO *, KF_INT);
+void	write_unum(IO *, KF_UINT);
 void	write_dnum(IO *, KF_LONG);
 void	write_dstack(IO *, Stack<KF_INT>);
 
diff --git a/linux/defs.h b/linux/defs.h
index edcbdb2..c007fee 100644
--- a/linux/defs.h
+++ b/linux/defs.h
@@ -5,8 +5,24 @@
 #include <stdint.h>
 
 typedef int32_t KF_INT;
+typedef uint32_t KF_UINT;
 typedef int64_t	KF_LONG;
+constexpr size_t dshift = (sizeof(KF_INT) * 8) - 1;
 
-constexpr uint8_t	STACK_SIZE = 128;
+typedef uintptr_t KF_ADDR;
+constexpr uint8_t STACK_SIZE = 128;
+constexpr size_t ARENA_SIZE = 65535;
+
+static inline KF_INT
+mask(size_t bits)
+{
+	KF_INT m = 0;
+
+	for (size_t i = 0; i < bits; i++) {
+		m += 1 << i;
+	}
+	
+	return m;
+}
 
 #endif
\ No newline at end of file
diff --git a/stack.h b/stack.h
index a4f31a8..b909dad 100644
--- a/stack.h
+++ b/stack.h
@@ -8,6 +8,7 @@ class Stack {
 public:
         bool   push(T val);
 	bool   pop(T *val);
+	bool   peek(T *val);
 	bool   get(size_t, T &);
 	bool   remove(size_t, T *);
 	size_t size(void) { return this->arrlen; }
@@ -44,6 +45,20 @@ Stack<T>::pop(T *val)
 	return true;
 }
 
+// peek returns false if there was a stack underflow.
+template <typename T>
+bool
+Stack<T>::peek(T *val)
+{
+	if (this->arrlen == 0) {
+		return false;
+	}
+
+	*val = this->arr[this->arrlen - 1];
+	return true;
+}
+
+
 // get returns false on invalid bounds.
 template <typename T>
 bool
diff --git a/system.cc b/system.cc
index aebd834..e3ab8de 100644
--- a/system.cc
+++ b/system.cc
@@ -8,6 +8,8 @@ constexpr static char   STATE_STR_STACK_OVERFLOW[] = "stack overflow";
 constexpr static char   STATE_STR_STACK_UNDERFLOW[] = "stack underflow";
 constexpr static char   STATE_STR_EXECUTION_FAILURE[] = "execution failure";
 constexpr static char	STATE_STR_UNKNOWN_WORD[] = "unknown word";
+constexpr static char	STATE_STR_RSTACK_OVERFLOW[] = "return stack overflow";
+constexpr static char	STATE_STR_RSTACK_UNDERFLOW[] = "return stack underflow";
 constexpr static char	STATE_STR_UNKNOWN_STATE[] = "undefined state";
 constexpr static char	STATE_STR_ERROR_CODE[] = " (error code ";
 
@@ -48,6 +50,14 @@ system_write_status(System *sys)
 		buf = (char *)(STATE_STR_UNKNOWN_WORD);
 		len = sizeof STATE_STR_UNKNOWN_WORD;
 		break;
+	case STATUS_RSTACK_OVERFLOW:
+		buf = (char *)(STATE_STR_RSTACK_OVERFLOW);
+		len = sizeof STATE_STR_RSTACK_OVERFLOW;
+		break;
+	case STATUS_RSTACK_UNDERFLOW:
+		buf = (char *)(STATE_STR_RSTACK_UNDERFLOW);
+		len = sizeof STATE_STR_RSTACK_UNDERFLOW;
+		break;
 	default:
 		buf = (char *)(STATE_STR_UNKNOWN_STATE);
 		len = sizeof STATE_STR_UNKNOWN_STATE;
diff --git a/system.h b/system.h
index 91aa1fa..79de2b3 100644
--- a/system.h
+++ b/system.h
@@ -10,16 +10,20 @@ typedef enum _SYS_STATUS : uint8_t {
 	STATUS_STACK_OVERFLOW = 1,
 	STATUS_STACK_UNDERFLOW = 2,
 	STATUS_EXECUTION_FAILURE = 3,
-	STATUS_UNKNOWN_WORD = 4
+	STATUS_UNKNOWN_WORD = 4,
+	STATUS_RSTACK_OVERFLOW = 5,
+	STATUS_RSTACK_UNDERFLOW = 6
 } SYS_STATUS;
 
 class Word;
 
 typedef struct _System {
 	Stack<KF_INT>	 dstack;
+	Stack<KF_ADDR>	 rstack;
 	IO		*interface;
 	Word		*dict;
 	SYS_STATUS	 status;
+	uint8_t		 arena[ARENA_SIZE];
 } System;
 
 void	system_clear_error(System *sys);
diff --git a/word.cc b/word.cc
index 399b275..9e09188 100644
--- a/word.cc
+++ b/word.cc
@@ -33,6 +33,51 @@ Builtin::match(struct Token *token)
 
 void
 Builtin::getname(char *buf, size_t *buflen)
+{
+	memcpy(buf, this->name, this->namelen);
+	*buflen = namelen;
+}
+
+
+Address::Address(const char *name, size_t namelen, Word *head, KF_ADDR addr)
+	: prev(head), addr(addr)
+{
+	memcpy(this->name, name, namelen);
+	this->namelen = namelen;
+}
+
+bool
+Address::eval(System *sys)
+{
+	KF_INT	a;
+
+	a = static_cast<KF_INT>(this->addr & mask(dshift));
+	if (!sys->dstack.push(a)) {
+		return false;
+	}
+
+	a = static_cast<KF_INT>((this->addr >> dshift) & mask(dshift));
+	if (!sys->dstack.push(a)) {
+		return false;
+	}
+
+	return true;
+}
+
+Word *
+Address::next(void)
+{
+	return this->prev;
+}
+
+bool
+Address::match(struct Token *token)
+{
+	return match_token(this->name, this->namelen, token->token, token->length);
+}
+
+void 
+Address::getname(char *buf, size_t *buflen)
 {
 	memcpy(buf, this->name, this->namelen);
 	*buflen = namelen;
diff --git a/word.h b/word.h
index 1989e88..03557df 100644
--- a/word.h
+++ b/word.h
@@ -14,6 +14,7 @@ public:
 	virtual Word *next(void) = 0;
 	virtual bool  match(struct Token *) = 0;
 	virtual void  getname(char *, size_t *) = 0;
+	virtual uintptr_t address(void) = 0;
 };
 
 class Builtin : public Word {
@@ -25,6 +26,7 @@ public:
 	Word *next(void);
 	bool  match(struct Token *);
 	void  getname(char *, size_t *);
+	uintptr_t address(void) { return reinterpret_cast<uintptr_t>(this); }
 private:
 	char		 name[MAX_TOKEN_LENGTH];
 	size_t		 namelen;
@@ -32,4 +34,21 @@ private:
 	bool		(*fun)(System *);
 };
 
+class Address : public Word {
+public:
+	~Address() {};
+	Address(const char *name, size_t namelen, Word *head, KF_ADDR addr);
+
+	bool eval(System *);
+	Word *next(void);
+	bool  match(struct Token *);
+	void  getname(char *, size_t *);
+	uintptr_t address(void) { return reinterpret_cast<uintptr_t>(this); }
+private:
+	char	 name[MAX_TOKEN_LENGTH];
+	size_t	 namelen;
+	Word	*prev;
+	KF_ADDR	 addr;
+};
+
 #endif // __KF_WORD_H__
\ No newline at end of file