diff --git a/interpreter/core_methods.c b/interpreter/core_methods.c
new file mode 100644
index 0000000..b63a863
--- /dev/null
+++ b/interpreter/core_methods.c
@@ -0,0 +1,360 @@
+#include "core_methods.h"
+
+#define BCI_CORE_REGISTER_CHECK(var) if(var > BCI_CORE_NUM_REG) return 1
+
+// #1 -> $0
+char bci_cm_ldi(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+
+	uint16_t arg;
+	char res;
+	res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+	if(res)
+	{
+		return res;
+	}
+
+	state->data_reg[small_arg] = arg;
+
+	return machine_state_t_default_afterexec(state, 1);
+}
+
+// @1 -> $0
+char bci_cm_ld(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+
+	uint16_t arg;
+	char res;
+	res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+	if(res)
+	{
+		return res;
+	}
+
+	res = machine_state_t_get_mem(state, arg, &arg);
+	if(res)
+	{
+		return res;
+	}
+	state->data_reg[small_arg] = arg;
+
+	return machine_state_t_default_afterexec(state, 1);
+}
+
+// $0 -> @1
+char bci_cm_st(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+	char res;
+
+	uint16_t arg;
+	res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+	if(res)
+	{
+		return res;
+	}
+
+	res = machine_state_t_set_mem(state, arg, state->data_reg[small_arg]);
+	if(res)
+	{
+		return res;
+	}
+
+	return machine_state_t_default_afterexec(state, 1);
+}
+
+// $0 + 1 -> $0
+char bci_cm_inc(uint8_t small_arg, machine_state_t state)
+{
+	int32_t result;
+	BCI_CORE_REGISTER_CHECK(small_arg);
+	result = state->data_reg[small_arg] + 1;
+	state->data_reg[small_arg] = result & 0xffff;
+	state->status_reg = result >> 16;
+	return machine_state_t_default_afterexec(state, 0);
+}
+
+// $0 - 1 -> $0
+char bci_cm_dec(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+	int32_t result = state->data_reg[small_arg] - 1;
+	state->data_reg[small_arg] = result & 0xffff;
+	state->status_reg = result >> 16;
+	return machine_state_t_default_afterexec(state, 0);
+}
+
+// $0 + $1 -> $0
+char bci_cm_add(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+	uint16_t arg;
+	char res;
+	res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+	if(res)
+	{
+		return res;
+	}
+
+	BCI_CORE_REGISTER_CHECK(arg);
+	int32_t result = state->data_reg[small_arg] + state->data_reg[arg];
+	state->data_reg[small_arg] = result & 0xffff;
+	state->status_reg = result >> 16;
+	
+	return machine_state_t_default_afterexec(state, 1);
+}
+
+
+// $0 - $1 -> $0
+char bci_cm_sub(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+	uint16_t arg;
+	char res;
+	res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+	if(res)
+	{
+		return res;
+	}
+
+	BCI_CORE_REGISTER_CHECK(arg);
+	int32_t result = state->data_reg[small_arg] - state->data_reg[arg];
+	
+	state->data_reg[small_arg] = result & 0xffff;
+	state->status_reg = result >> 16;
+
+	return machine_state_t_default_afterexec(state, 1);
+}
+
+
+// $0 * $1 -> $0
+char bci_cm_mul(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+	uint16_t arg;
+	char res;
+	res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+	if(res)
+	{
+		return res;
+	}
+
+	BCI_CORE_REGISTER_CHECK(arg);
+	int32_t result = state->data_reg[small_arg] * state->data_reg[arg];
+	state->data_reg[small_arg] = result & 0xffff;
+	state->status_reg = result >> 16;
+	return machine_state_t_default_afterexec(state, 1);
+}
+
+// $0 / $1 -> $0
+char bci_cm_div(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+	uint16_t arg;
+	char res;
+	res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+	if(res)
+	{
+		return res;
+	}
+
+	BCI_CORE_REGISTER_CHECK(arg);
+	int32_t result = state->data_reg[small_arg] / state->data_reg[arg];
+	state->data_reg[small_arg] = result & 0xffff;
+	state->status_reg = result >> 16;
+	return machine_state_t_default_afterexec(state, 1);
+}
+
+
+// if($0 > 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_gt(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+
+	if(state->data_reg[small_arg] > 0)
+	{
+		state->status_reg = 1;
+	}
+	else
+	{
+		state->status_reg = 0;
+	}
+	return machine_state_t_default_afterexec(state, 0);
+}
+
+// if($0 >= 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_ge(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+
+	if(state->data_reg[small_arg] >= 0)
+	{
+		state->status_reg = 1;
+	}
+	else
+	{
+		state->status_reg = 0;
+	}
+	return machine_state_t_default_afterexec(state, 0);
+}
+// if($0 < 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_lt(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+
+	if(state->data_reg[small_arg] < 0)
+	{
+		state->status_reg = 1;
+	}
+	else
+	{
+		state->status_reg = 0;
+	}
+	return machine_state_t_default_afterexec(state, 0);
+}
+// if($0 <= 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_le(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+
+	if(state->data_reg[small_arg] <= 0)
+	{
+		state->status_reg = 1;
+	}
+	else
+	{
+		state->status_reg = 0;
+	}
+	return machine_state_t_default_afterexec(state, 0);
+}
+// if($0 == 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_eq(uint8_t small_arg, machine_state_t state)
+{
+	BCI_CORE_REGISTER_CHECK(small_arg);
+
+	if(state->data_reg[small_arg] == 0)
+	{
+		state->status_reg = 1;
+	}
+	else
+	{
+		state->status_reg = 0;
+	}
+	return machine_state_t_default_afterexec(state, 0);
+}
+
+// #1 -> $pc; 0 -> $st_reg
+char bci_cm_jmp(uint8_t small_arg, machine_state_t state)
+{
+	uint16_t arg;
+	char res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+
+	if(res)
+	{
+		return res;
+	}
+
+	state->program_counter = arg;
+	return 0;
+}
+
+// if($st_reg): #1 -> $pc; 0 -> $st_reg
+// else: do nothing
+char bci_cm_cjmp(uint8_t small_arg, machine_state_t state)
+{
+	uint16_t arg;
+	char res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+
+	if(res)
+	{
+		return res;
+	}
+
+	if(state->status_reg)
+	{
+		state->program_counter = arg;
+		return 0;
+	}
+
+	return machine_state_t_default_afterexec(state, 1);
+}
+// $pc -> @stack
+// #1 -> $pc
+char bci_cm_call(uint8_t small_arg, machine_state_t state)
+{
+	uint16_t arg;
+	char res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+
+	if(res)
+	{
+		return res;
+	}
+
+	res = bci_stack_t_push(&(state->stack), state->program_counter);
+	if(res)
+	{
+		return res;
+	}
+	state->program_counter = arg;
+	return 0;
+}
+// if($st_reg): $pc -> @stack; #1 -> $pc; 0 -> $st_reg
+// else: do nothing
+char bci_cm_ccall(uint8_t small_arg, machine_state_t state)
+{
+	uint16_t arg;
+	char res = machine_state_t_get_word(state, state->program_counter + 1, &arg);
+
+	if(res)
+	{
+		return res;
+	}
+
+	if(state->status_reg)
+	{
+		state->program_counter = arg;
+		res = bci_stack_t_push(&(state->stack), state->program_counter);
+		if(res)
+		{
+			return res;
+		}
+		return 0;
+	}
+
+	return machine_state_t_default_afterexec(state, 1);
+}
+// @stack -> $pc
+char bci_cm_ret(uint8_t small_arg, machine_state_t state)
+{
+	uint16_t result;
+	char res = bci_stack_t_pop(&(state->stack), &result);
+	if(res)
+	{
+		return res;
+	}
+
+	state->program_counter = result;
+	return 0;
+}
+
+// 0 -> $st_reg
+char bci_cm_cl(uint8_t small_arg, machine_state_t state)
+{
+	state->status_reg = 0;
+	return machine_state_t_default_afterexec(state, 0);
+}
+
+// 1 -> $su_reg
+char bci_cm_stop(uint8_t small_arg, machine_state_t state)
+{
+	state->shutdown_reg = 0;
+	return machine_state_t_default_afterexec(state, 0);
+}
+
diff --git a/interpreter/core_methods.h b/interpreter/core_methods.h
new file mode 100644
index 0000000..b7fdd08
--- /dev/null
+++ b/interpreter/core_methods.h
@@ -0,0 +1,110 @@
+#ifndef bci_core_methods_h__
+#define bci_core_methods_h__
+#include "interpreter.h"
+
+
+/*
+ * This library brings a set of essential core methods.
+ * */
+
+
+/*
+ * Naming conventions:
+ *
+ * x = 0, 1, 2, 3...: arguments.
+ *     0: small_arg (6 bit)
+ *     1, 2, ...: 16 bit optional arguments
+ *
+ * $x: value of data register x
+ * @x: value of memory word x
+ * #x: value of argument x
+ * 0, 1, 2, ...: integer 0, 1, 2, ...
+ *
+ * -> write result in register/word on the right
+ *
+ * st_reg: status register
+ * su_reg: shutdown register
+ * pc: program counter
+ *
+ * stack: the builtin stack
+ * */
+
+// #1 -> $0
+char bci_cm_ldi(uint8_t small_arg, machine_state_t state);
+
+// @1 -> $0
+char bci_cm_ld(uint8_t small_arg, machine_state_t state);
+
+// $0 -> @1
+char bci_cm_st(uint8_t small_arg, machine_state_t state);
+
+
+// NOTES on inc, dec, add, sub, mul, div:
+//
+// These methods will store the overflow-word in $st_reg.
+
+
+// $0 + 1 -> $0
+char bci_cm_inc(uint8_t small_arg, machine_state_t state);
+
+// $0 - 1 -> $0
+char bci_cm_dec(uint8_t small_arg, machine_state_t state);
+
+// $0 + $1 -> $0
+char bci_cm_add(uint8_t small_arg, machine_state_t state);
+
+// $0 - $1 -> $0
+char bci_cm_sub(uint8_t small_arg, machine_state_t state);
+
+// $0 * $1 -> $0
+char bci_cm_mul(uint8_t small_arg, machine_state_t state);
+
+// $0 / $1 -> $0
+char bci_cm_div(uint8_t small_arg, machine_state_t state);
+
+// if($0 > 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_gt(uint8_t small_arg, machine_state_t state);
+
+// if($0 >= 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_ge(uint8_t small_arg, machine_state_t state);
+
+// if($0 < 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_lt(uint8_t small_arg, machine_state_t state);
+
+// if($0 <= 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_le(uint8_t small_arg, machine_state_t state);
+
+// if($0 == 0): 1 -> $st_reg
+// else: 0 -> $st_reg
+char bci_cm_eq(uint8_t small_arg, machine_state_t state);
+
+// #1 -> $pc
+char bci_cm_jmp(uint8_t small_arg, machine_state_t state);
+
+// if($st_reg): #1 -> $pc
+// else: do nothing
+char bci_cm_cjmp(uint8_t small_arg, machine_state_t state);
+
+// $pc -> @stack
+// #1 -> $pc
+char bci_cm_call(uint8_t small_arg, machine_state_t state);
+
+// if($st_reg): $pc -> @stack; #1 -> $pc
+// else: do nothing
+char bci_cm_ccall(uint8_t small_arg, machine_state_t state);
+
+// @stack -> $pc
+char bci_cm_ret(uint8_t small_arg, machine_state_t state);
+
+// 0 -> $st_reg
+char bci_cm_cl(uint8_t small_arg, machine_state_t state);
+
+// 1 -> $su_reg
+char bci_cm_stop(uint8_t small_arg, machine_state_t state);
+
+
+#endif
diff --git a/interpreter/test/Makefile b/interpreter/test/Makefile
new file mode 100644
index 0000000..6703b38
--- /dev/null
+++ b/interpreter/test/Makefile
@@ -0,0 +1,14 @@
+CC=gcc
+
+all: test_interpreter
+
+interpreter: clean
+	$(CC) -g ../../stack.c ../interpreter.c ../core_methods.c ../../method_dispatcher/method_dispatcher.c test_interpreter.c -o interpreter
+
+test_interpreter: interpreter
+	valgrind ./interpreter
+
+
+
+clean:
+
diff --git a/interpreter/test/test_interpreter.c b/interpreter/test/test_interpreter.c
new file mode 100644
index 0000000..5793f0c
--- /dev/null
+++ b/interpreter/test/test_interpreter.c
@@ -0,0 +1,64 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include "../interpreter.h"
+#include "../core_methods.h"
+#include "../../method_dispatcher/method_dispatcher.h"
+
+size_t copy_cache(uint16_t * cache
+		, uint16_t offset
+		, size_t cache_size
+		, void * cache_function_data);
+
+int main(void)
+{
+	dispatch_tree_t tree = dispatch_tree_t_new();
+	dispatch_tree_autoinserter_t inserter = dispatch_tree_autoinserter_t_new(tree);
+	uint16_t ldi = dispatch_tree_autoinserter_t_insert(inserter, (bci_core_method_t) bci_cm_ldi);
+	uint16_t add = dispatch_tree_autoinserter_t_insert(inserter, (bci_core_method_t) bci_cm_add);
+
+	uint16_t * program = calloc(sizeof(uint16_t), 20);
+	program[0] = ldi;
+	program[1] = 0xfefe;
+	program[2] = ldi | 1;
+	program[3] = 2;
+	program[4] = ldi | 2;
+	program[5] = 3;
+	program[6] = add | 1;
+	program[7] = 2;
+
+	machine_state_t state = machine_state_t_new(
+			program
+			, 8
+			, 20
+			, 20
+			, copy_cache
+			, tree);
+
+	machine_state_t_exec_cycle(state);
+	machine_state_t_exec_cycle(state);
+	machine_state_t_exec_cycle(state);
+	machine_state_t_exec_cycle(state);
+	printf("data_reg[0]: %x\n", state->data_reg[0]);
+	printf("data_reg[1]: %x\n", state->data_reg[1]);
+	printf("data_reg[2]: %x\n", state->data_reg[2]);
+	printf("program_counter: %d\n", state->program_counter);
+	dispatch_tree_autoinserter_t_del(inserter);
+	machine_state_t_del(state);
+	free(program);
+	return 0;
+}
+
+size_t copy_cache(uint16_t * cache
+		, uint16_t offset
+		, size_t cache_size
+		, void * cache_function_data)
+{
+	size_t i;
+	for(i = 0; i < cache_size; i++)
+	{
+		printf("\tCP [%zd]->[%zd]: %x\n", i + offset, i, ((uint16_t *) cache_function_data)[i + offset]);
+		cache[i] = ((uint16_t *) cache_function_data)[i + offset];
+	}
+	return i;
+}
+