diff --git a/6502emu/src/main.rs b/6502emu/src/main.rs
index 0b777a1..14158cb 100644
--- a/6502emu/src/main.rs
+++ b/6502emu/src/main.rs
@@ -1,69 +1,141 @@
-struct Processor {
-	accumulator:     u8,
-	index_x:         u8,
-	index_y:         u8,
-	stack_pointer:   u8,
-	program_counter: u16,
-	status:          u8,
-}
+mod Registers {
+	// Each status flag should be 0 or 1.
+	pub struct Status {
+		pub carry:        u8,
+		pub zero:         u8,
+		pub interrupt:    u8,
+		pub decimal_mode: u8,
+		pub brk:          u8,
+		pub unused:       u8,
+		pub overflow:     u8,
+		pub sign:         u8
+	}
 
-impl Processor {
-}
-
-#[deriving(PartialEq)]
-#[deriving(Eq)]
-#[deriving(PartialOrd)]
-#[deriving(Ord)]
-struct Address(u16);
-
-impl Address {
-	fn to_int(&self) -> u16 {
-		match *self {
-			Address(address_) => address_
+	impl Status {
+		pub fn to_byte(&self) -> u8 {
+			  self.carry        << 0
+			| self.zero         << 1
+			| self.interrupt    << 2
+			| self.decimal_mode << 3
+			| self.brk          << 4
+			| self.unused       << 5
+			| self.overflow     << 6
+			| self.sign         << 7
 		}
 	}
 
-	fn min() -> Address { Address(0x0100) }
-	fn max() -> Address { Address(0x01ff) }
+	pub struct Registers {
+		pub accumulator:     i8,
+		pub index_x:         i8,
+		pub index_y:         i8,
+		pub stack_pointer:   u8,
+		pub program_counter: u16,
+		pub status:          Status
+	}
 
-	fn is_valid(&self) -> bool {
-		Address::min() <= *self && *self <= Address::max()
+	impl Registers {
 	}
 }
 
-struct Memory {
-	bytes: [u8,.. 256]
+mod Address {
+	#[deriving(PartialEq)]
+	#[deriving(Eq)]
+	#[deriving(PartialOrd)]
+	#[deriving(Ord)]
+	pub struct Address(u16);
+
+	impl Address {
+		/* TODO akeeton: Hide struct Address(u16) "constructor."
+		pub fn new(address_: u16) -> Address {
+			Address(address_)
+		}
+		*/
+
+		pub fn to_int(&self) -> u16 {
+			match *self {
+				Address(address_) => address_
+			}
+		}
+
+		pub fn min() -> Address { Address(0x0100) }
+		pub fn max() -> Address { Address(0x01ff) }
+
+		pub fn is_valid(&self) -> bool {
+			Address::min() <= *self && *self <= Address::max()
+		}
+	}
 }
 
-impl Memory {
-	fn address_to_byte_offset(address: &Address) -> uint {
-		(address.to_int() - Address::min().to_int()) as uint
+mod Memory {
+	use Address::Address;
+
+	pub struct Memory {
+		bytes: [u8,.. 256]
 	}
 
-	fn get_byte(&self, address: &Address) -> u8 {
-		if !address.is_valid()
-		{
-			fail!("Invalid address.");
+	impl Memory {
+		fn address_to_byte_offset(address: &Address) -> uint {
+			(address.to_int() - Address::min().to_int()) as uint
 		}
-		else
-		{
-			return self.bytes[Memory::address_to_byte_offset(address)];
+
+		pub fn get_byte(&self, address: &Address) -> u8 {
+			if !address.is_valid()
+			{
+				fail!("Invalid address.");
+			}
+			else
+			{
+				return self.bytes[Memory::address_to_byte_offset(address)];
+			}
+		}
+
+		// Sets the byte at the given address to the given value and returns the
+		// previous value at the address.
+		pub fn set_byte(&mut self, address: &Address, value: u8) -> u8 {
+			if !address.is_valid()
+			{
+				fail!("Invalid address.");
+			}
+			else
+			{
+				let old_value = self.get_byte(address);
+				self.bytes[Memory::address_to_byte_offset(address)] = value;
+
+				return old_value;
+			}
 		}
 	}
+}
 
-	// Sets the byte at the given address to the given value and returns the
-	// previous value at the address. 
-	fn set_byte(&mut self, address: &Address, value: u8) -> u8 {
-		if !address.is_valid()
-		{
-			fail!("Invalid address.");
-		}
-		else
-		{
-			let old_value = self.get_byte(address);
-			self.bytes[Memory::address_to_byte_offset(address)] = value;
+mod Machine {
+	use Registers::Registers;
+	use Address::Address;
+	use Memory::Memory;
 
-			return old_value;
+	struct Machine {
+		registers: Registers,
+		memory:    Memory
+	}
+
+	impl Machine {
+		// TODO akeeton: Implement binary-coded decimal.
+		pub fn add_with_carry(&mut self, value: i8) {
+			let a: int = self.registers.accumulator  as int;
+			let c: int = self.registers.status.carry as int;
+
+			let a_new_full: int = a + c + value as int;
+			let a_new:      i8  = a_new_full as i8;
+
+			self.registers.accumulator     = a_new;
+			self.registers.status.carry    = if a_new_full == a_new as int { 0 } else { 1 };
+			self.registers.status.zero     = if a_new == 0 { 1 } else { 0 };
+			self.registers.status.sign     = if a_new  < 0 { 1 } else { 0 };
+			self.registers.status.overflow =
+				if (a < 0 && value < 0 && a_new >= 0)
+				|| (a > 0 && value > 0 && a_new <= 0)
+				{ 1 }
+				else
+				{ 0 }
 		}
 	}
 }