initial

.gitignore

@@ -0,0 +1,2 @@
+.idea/
+cmake-build-debug/

CMakeLists.txt

@@ -0,0 +1,33 @@
+cmake_minimum_required(VERSION 3.13)
+project(6502_emulator)
+
+set(CMAKE_CXX_STANDARD 14)
+
+configure_file(CMakeLists.txt.in googletest-download/CMakeLists.txt)
+execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
+        RESULT_VARIABLE result
+        WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/googletest-download )
+if(result)
+    message(FATAL_ERROR "CMake step for googletest failed: ${result}")
+endif()
+execute_process(COMMAND ${CMAKE_COMMAND} --build .
+        RESULT_VARIABLE result
+        WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/googletest-download )
+if(result)
+    message(FATAL_ERROR "Build step for googletest failed: ${result}")
+endif()
+
+set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+
+add_subdirectory(${CMAKE_CURRENT_BINARY_DIR}/googletest-src
+        ${CMAKE_CURRENT_BINARY_DIR}/googletest-build
+        EXCLUDE_FROM_ALL)
+
+file(GLOB_RECURSE test_src "test/**.h" "test/**.cpp" "src/**.h" "src/**.cpp")
+list(FILTER test_src EXCLUDE REGEX ".*/6502-emulator/src/main.cpp$")
+add_executable(6502_emulator_test ${test_src} test/machine-test.cpp test/flags-opcode-handler-test.cpp)
+target_link_libraries(6502_emulator_test gtest_main)
+add_test(NAME run_tests COMMAND 6502_emulator_test)
+
+file(GLOB_RECURSE emulator_src "src/**.h" "src/**.cpp")
+add_executable(6502_emulator ${emulator_src})

CMakeLists.txt.in

@@ -0,0 +1,15 @@
+cmake_minimum_required(VERSION 3.13)
+
+project(googletest-download NONE)
+
+include(ExternalProject)
+ExternalProject_Add(googletest
+        GIT_REPOSITORY    https://github.com/google/googletest.git
+        GIT_TAG           master
+        SOURCE_DIR        "${CMAKE_CURRENT_BINARY_DIR}/googletest-src"
+        BINARY_DIR        "${CMAKE_CURRENT_BINARY_DIR}/googletest-build"
+        CONFIGURE_COMMAND ""
+        BUILD_COMMAND     ""
+        INSTALL_COMMAND   ""
+        TEST_COMMAND      ""
+        )

src/instruction/instruction-executor.cpp

@@ -0,0 +1,38 @@
+#include "instruction-executor.h"
+#include <stdexcept>
+
+#include <iostream>
+
+void dump_cpu_state(shared_ptr<RegisterManager> reg_man) {
+    cout << "--------------" << endl;
+    cout << "A=0x" << hex << (int) reg_man->get_accumulator()->get_value() <<
+         " X=0x" << hex << (int) reg_man->get_x_index()->get_value() <<
+         " Y=0x" << hex << (int) reg_man->get_y_index()->get_value() << endl;
+
+    cout << "SP=0x" << hex << (int) reg_man->get_stack_pointer()->get_value() <<
+         " PC=0x" << hex << (int) reg_man->get_program_counter()->get_value() << endl;
+
+    cout << "NV-BDIZC" << endl <<
+         reg_man->get_status_register()->get_value() << endl;
+}
+
+InstructionExecutor::InstructionExecutor(shared_ptr<Program> program, shared_ptr<RegisterManager> reg_man,
+                                         shared_ptr<OpcodeHandlerDirectory> opcode_handler_dir) {
+    this->program = program;
+    this->reg_man = reg_man;
+    this->opcode_handler_dir = opcode_handler_dir;
+}
+
+void InstructionExecutor::execute() {
+    auto pc = reg_man->get_program_counter();
+
+    do {
+        auto opcode = program->get_byte_at(pc->get_value());
+        auto handler = opcode_handler_dir->get_handler(opcode);
+
+        handler->execute();
+
+        dump_cpu_state(reg_man);
+
+    } while (pc->get_value() < program->get_size());
+}

src/instruction/instruction-executor.h

@@ -0,0 +1,27 @@
+#ifndef INC_6502_EMULATOR_INSTRUCTION_EXECUTOR_H
+#define INC_6502_EMULATOR_INSTRUCTION_EXECUTOR_H
+
+#include "../program.h"
+#include "../register/register-manager.h"
+#include "../opcode/opcode-handler-directory.h"
+
+#include <memory>
+#include <vector>
+
+using namespace std;
+
+class InstructionExecutor {
+public:
+    explicit InstructionExecutor(shared_ptr<Program> program, shared_ptr<RegisterManager> reg_man,
+            shared_ptr<OpcodeHandlerDirectory> opcode_handler_dir);
+
+    void execute();
+
+private:
+    shared_ptr<Program> program;
+    shared_ptr<RegisterManager> reg_man;
+    shared_ptr<OpcodeHandlerDirectory> opcode_handler_dir;
+};
+
+
+#endif //INC_6502_EMULATOR_INSTRUCTION_EXECUTOR_H

src/machine.cpp

@@ -0,0 +1,24 @@
+#include "machine.h"
+
+#include <iostream>
+
+Machine::Machine(shared_ptr<Program> program) {
+    this->program = program;
+    memory = make_shared<Memory>(Memory());
+    reg_man = make_shared<RegisterManager>(RegisterManager());
+    opcode_handler_dir = make_shared<OpcodeHandlerDirectory>(OpcodeHandlerDirectory(program, reg_man));
+    instruction_executor =
+            make_unique<InstructionExecutor>(InstructionExecutor(program, reg_man, opcode_handler_dir));
+}
+
+shared_ptr<Memory> Machine::get_memory() {
+    return memory;
+}
+
+shared_ptr<RegisterManager> Machine::get_reg_man() {
+    return reg_man;
+}
+
+void Machine::execute() {
+    instruction_executor->execute();
+}

src/machine.h

@@ -0,0 +1,31 @@
+#ifndef INC_6502_EMULATOR_MACHINE_H
+#define INC_6502_EMULATOR_MACHINE_H
+
+#include "program.h"
+#include "memory.h"
+#include "register/register-manager.h"
+#include "opcode/opcode-handler-directory.h"
+#include "instruction/instruction-executor.h"
+#include <vector>
+
+using namespace std;
+
+class Machine {
+public:
+    explicit Machine(shared_ptr<Program> program);
+
+    shared_ptr<RegisterManager> get_reg_man();
+    shared_ptr<Memory> get_memory();
+
+    void execute();
+
+private:
+    shared_ptr<Program> program;
+    shared_ptr<Memory> memory;
+    shared_ptr<RegisterManager> reg_man;
+    shared_ptr<OpcodeHandlerDirectory> opcode_handler_dir;
+    shared_ptr<InstructionExecutor> instruction_executor;
+};
+
+
+#endif //INC_6502_EMULATOR_MACHINE_H

src/main.cpp

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+#include "register/register-manager.h"
+
+#include <iostream>
+#include <memory>
+
+using namespace std;
+
+void stack_test(string astring) {
+    astring.push_back('x');
+}
+
+void heap_test(shared_ptr<string> astring){
+    astring->push_back('y');
+}
+
+int main() {
+    auto reg = unique_ptr<Register<uint8_t>>(new Register<uint8_t>("PC"));
+
+    cout << "Register: " << reg->get_name() << " " << to_string(56) << endl;
+
+    string astr = "hello";
+    shared_ptr<string> bstr = make_shared<string>("there");
+
+    cout << astr << " - " << bstr->c_str() << endl;
+
+    stack_test(astr);
+    heap_test(bstr);
+
+    cout << astr << " - " << bstr->c_str() << endl;
+
+    auto reg_man = new RegisterManager();
+    auto accum = reg_man->get_accumulator();
+
+    cout << "****** " << accum->get_name() << " ******" << endl;
+    cout << "****** " << reg_man->get_x_index()->get_name() << " ******" << endl;
+    cout << "****** " << reg_man->get_y_index()->get_name() << " ******" << endl;
+    cout << "****** " << reg_man->get_stack_pointer()->get_name() << " ******" << endl;
+    cout << "****** " << reg_man->get_status_register()->get_name() << " ******" << endl;
+    cout << "****** " << reg_man->get_program_counter()->get_name() << " ******" << endl;
+
+    return 0;
+}

src/memory.cpp

@@ -0,0 +1,14 @@
+#include "memory.h"
+#include <stdexcept>
+
+Memory::Memory() {
+    bytes = make_shared<vector<uint8_t>>(vector<uint8_t>((1024 * 64) - 1));
+}
+
+uint8_t Memory::get_byte_at(uint16_t index) {
+    auto size = bytes->size();
+    if (size == 0 || bytes->size() - 1 < index)
+        throw runtime_error("Attempted to read past end of memory");
+
+    return bytes->at(index);
+}

src/memory.h

@@ -0,0 +1,21 @@
+#ifndef INC_6502_EMULATOR_MEMORY_H
+#define INC_6502_EMULATOR_MEMORY_H
+
+
+#include <memory>
+#include <vector>
+
+using namespace std;
+
+class Memory {
+public:
+    explicit Memory();
+
+    uint8_t get_byte_at(uint16_t index);
+
+private:
+    shared_ptr<vector<uint8_t>> bytes;
+};
+
+
+#endif //INC_6502_EMULATOR_MEMORY_H

src/opcode/handler/flag-opcode-handler.cpp

@@ -0,0 +1,48 @@
+#include "flag-opcode-handler.h"
+
+#include <stdexcept>
+#include <sstream>
+
+const uint8_t FlagOpcodeHandler::CLC;
+const uint8_t FlagOpcodeHandler::SEC;
+const uint8_t FlagOpcodeHandler::CLI;
+const uint8_t FlagOpcodeHandler::SEI;
+const uint8_t FlagOpcodeHandler::CLV;
+const uint8_t FlagOpcodeHandler::CLD;
+const uint8_t FlagOpcodeHandler::SED;
+
+void FlagOpcodeHandler::execute() {
+    auto instructionIndex = reg_man->get_program_counter()->get_value();
+    auto opcode = program->get_byte_at(instructionIndex);
+    auto statusReg = reg_man->get_status_register();
+
+    switch (opcode) {
+        case CLC:
+            statusReg->set_carry(false);
+            break;
+        case SEC:
+            statusReg->set_carry(true);
+            break;
+        case CLI:
+            statusReg->set_interupt_disable(false);
+            break;
+        case SEI:
+            statusReg->set_interupt_disable(true);
+            break;
+        case CLV:
+            statusReg->set_overflow(false);
+            break;
+        case CLD:
+            statusReg->set_decimal(false);
+            break;
+        case SED:
+            statusReg->set_decimal(true);
+            break;
+        default:
+            stringstream stream;
+            stream << "Unexpected opcode 0x" << hex << opcode;
+            throw runtime_error(stream.str());
+    }
+
+    move_program_counter(1);
+}

src/opcode/handler/flag-opcode-handler.h

@@ -0,0 +1,31 @@
+#ifndef INC_6502_EMULATOR_FLAG_OPCODE_HANDLER_H
+#define INC_6502_EMULATOR_FLAG_OPCODE_HANDLER_H
+
+#include "../../program.h"
+#include "../opcode-handler.h"
+
+class FlagOpcodeHandler : public OpcodeHandler {
+public:
+    static const uint8_t CLC = 0x18;
+    static const uint8_t SEC = 0x38;
+    static const uint8_t CLI = 0x58;
+    static const uint8_t SEI = 0x78;
+    static const uint8_t CLV = 0xB8;
+    static const uint8_t CLD = 0xD8;
+    static const uint8_t SED = 0xF8;
+
+    explicit FlagOpcodeHandler(shared_ptr<Program> program, shared_ptr<RegisterManager> reg_man) :
+            OpcodeHandler(program, reg_man) {
+        handled_opcodes->push_back(CLC);
+        handled_opcodes->push_back(SEC);
+        handled_opcodes->push_back(CLI);
+        handled_opcodes->push_back(SEI);
+        handled_opcodes->push_back(CLV);
+        handled_opcodes->push_back(CLD);
+        handled_opcodes->push_back(SED);
+    }
+
+    virtual void execute() override;
+};
+
+#endif //INC_6502_EMULATOR_FLAG_OPCODE_HANDLER_H

src/opcode/handler/ldx-opcode-handler.cpp

@@ -0,0 +1,30 @@
+#include "ldx-opcode-handler.h"
+#include <sstream>
+
+const uint8_t LdxOpcodeHandler::IMMEDIATE;
+const uint8_t LdxOpcodeHandler::ZERO_PAGE;
+const uint8_t LdxOpcodeHandler::ZERO_PAGE_X;
+const uint8_t LdxOpcodeHandler::ABSOLUTE;
+const uint8_t LdxOpcodeHandler::ABSOLUTE_X;
+const uint8_t LdxOpcodeHandler::ABSOLUTE_Y;
+const uint8_t LdxOpcodeHandler::INDIRECT_X;
+const uint8_t LdxOpcodeHandler::INDIRECT_Y;
+
+void LdxOpcodeHandler::execute() {
+    auto instructionIndex = reg_man->get_program_counter()->get_value();
+    auto opcode = program->get_byte_at(instructionIndex);
+    auto byte2 = program->get_byte_at(instructionIndex + 1);
+    auto accumulator = reg_man->get_accumulator();
+
+    switch (opcode) {
+        case IMMEDIATE:
+            accumulator->set_value(byte2);
+            move_program_counter(2);
+            break;
+
+        default:
+            stringstream stream;
+            stream << "Unexpected opcode 0x" << hex << opcode;
+            throw runtime_error(stream.str());
+    }
+}

src/opcode/handler/ldx-opcode-handler.h

@@ -0,0 +1,33 @@
+#ifndef INC_6502_EMULATOR_LDX_OPCODE_HANDLER_H
+#define INC_6502_EMULATOR_LDX_OPCODE_HANDLER_H
+
+#include "../../program.h"
+#include "../opcode-handler.h"
+
+class LdxOpcodeHandler : public OpcodeHandler {
+public:
+    static const uint8_t IMMEDIATE = 0xA9;
+    static const uint8_t ZERO_PAGE = 0xA5;
+    static const uint8_t ZERO_PAGE_X = 0xB5;
+    static const uint8_t ABSOLUTE = 0xAD;
+    static const uint8_t ABSOLUTE_X = 0xBD;
+    static const uint8_t ABSOLUTE_Y = 0xB9;
+    static const uint8_t INDIRECT_X = 0xA1;
+    static const uint8_t INDIRECT_Y = 0xB1;
+
+    explicit LdxOpcodeHandler(shared_ptr<Program> program, shared_ptr<RegisterManager> reg_man) :
+            OpcodeHandler(program, reg_man) {
+        handled_opcodes->push_back(IMMEDIATE);
+        handled_opcodes->push_back(ZERO_PAGE);
+        handled_opcodes->push_back(ZERO_PAGE_X);
+        handled_opcodes->push_back(ABSOLUTE);
+        handled_opcodes->push_back(ABSOLUTE_X);
+        handled_opcodes->push_back(ABSOLUTE_Y);
+        handled_opcodes->push_back(INDIRECT_X);
+        handled_opcodes->push_back(INDIRECT_Y);
+    }
+
+    virtual void execute() override;
+};
+
+#endif //INC_6502_EMULATOR_LDX_OPCODE_HANDLER_H

src/opcode/handler/register-opcode-handler.cpp

@@ -0,0 +1,54 @@
+#include "register-opcode-handler.h"
+
+#include <stdexcept>
+#include <sstream>
+
+const uint8_t RegisterOpcodeHandler::TAX;
+const uint8_t RegisterOpcodeHandler::TXA;
+const uint8_t RegisterOpcodeHandler::DEX;
+const uint8_t RegisterOpcodeHandler::INX;
+const uint8_t RegisterOpcodeHandler::TAY;
+const uint8_t RegisterOpcodeHandler::TYA;
+const uint8_t RegisterOpcodeHandler::DEY;
+const uint8_t RegisterOpcodeHandler::INY;
+
+void RegisterOpcodeHandler::execute() {
+    auto instructionIndex = reg_man->get_program_counter()->get_value();
+    auto opcode = program->get_byte_at(instructionIndex);
+    auto accumulator = reg_man->get_accumulator();
+    auto x_index = reg_man->get_x_index();
+    auto y_index = reg_man->get_y_index();
+
+    switch (opcode) {
+        case TAX:
+            x_index->set_value(accumulator->get_value());
+            break;
+        case TXA:
+            accumulator->set_value(x_index->get_value());
+            break;
+        case DEX:
+            x_index->set_value(x_index->get_value() - 1);
+            break;
+        case INX:
+            x_index->set_value(x_index->get_value() + 1);
+            break;
+        case TAY:
+            y_index->set_value(accumulator->get_value());
+            break;
+        case TYA:
+            accumulator->set_value(y_index->get_value());
+            break;
+        case DEY:
+            y_index->set_value(y_index->get_value() - 1);
+            break;
+        case INY:
+            y_index->set_value(y_index->get_value() + 1);
+            break;
+        default:
+            stringstream stream;
+            stream << "Unexpected opcode 0x" << hex << opcode;
+            throw runtime_error(stream.str());
+    }
+
+    move_program_counter(1);
+}

src/opcode/handler/register-opcode-handler.h

@@ -0,0 +1,34 @@
+#ifndef INC_6502_EMULATOR_REGISTER_OPCODE_HANDLER_H
+#define INC_6502_EMULATOR_REGISTER_OPCODE_HANDLER_H
+
+#include "../../program.h"
+#include "../opcode-handler.h"
+
+class RegisterOpcodeHandler : public OpcodeHandler {
+public:
+    static const uint8_t TAX = 0xAA;
+    static const uint8_t TXA = 0x8A;
+    static const uint8_t DEX = 0xCA;
+    static const uint8_t INX = 0xE8;
+    static const uint8_t TAY = 0xA8;
+    static const uint8_t TYA = 0x98;
+    static const uint8_t DEY = 0x88;
+    static const uint8_t INY = 0xC8;
+
+    explicit RegisterOpcodeHandler(shared_ptr<Program> program, shared_ptr<RegisterManager> reg_man) :
+            OpcodeHandler(program, reg_man) {
+        handled_opcodes->push_back(TAX);
+        handled_opcodes->push_back(TXA);
+        handled_opcodes->push_back(DEX);
+        handled_opcodes->push_back(INX);
+        handled_opcodes->push_back(TAY);
+        handled_opcodes->push_back(TYA);
+        handled_opcodes->push_back(DEY);
+        handled_opcodes->push_back(INY);
+    }
+
+    virtual void execute() override;
+};
+
+
+#endif //INC_6502_EMULATOR_REGISTER_OPCODE_HANDLER_H

src/opcode/opcode-handler-directory.cpp

@@ -0,0 +1,31 @@
+#include "opcode-handler-directory.h"
+#include "handler/flag-opcode-handler.h"
+#include "handler/register-opcode-handler.h"
+#include "handler/ldx-opcode-handler.h"
+
+#include <sstream>
+#include <stdexcept>
+
+OpcodeHandlerDirectory::OpcodeHandlerDirectory(shared_ptr<Program> program, shared_ptr<RegisterManager> reg_man) {
+    handlers = make_unique<unordered_map<uint8_t, shared_ptr<OpcodeHandler>>>();
+
+    register_handler(make_shared<FlagOpcodeHandler>(program, reg_man));
+    register_handler(make_shared<RegisterOpcodeHandler>(program, reg_man));
+    register_handler(make_shared<LdxOpcodeHandler>(program, reg_man));
+}
+
+void OpcodeHandlerDirectory::register_handler(shared_ptr<OpcodeHandler> handler) {
+    for (auto opcode: *handler->get_handled_opcodes()) {
+        handlers->insert({opcode, handler});
+    }
+}
+
+shared_ptr<OpcodeHandler> OpcodeHandlerDirectory::get_handler(uint8_t opcode) {
+    if (handlers->find(opcode) == handlers->end()) {
+        stringstream stream;
+        stream << "No handler registered for opcode 0x" << hex << opcode;
+        throw runtime_error(stream.str());
+    }
+
+    return handlers->at(opcode);
+}

src/opcode/opcode-handler-directory.h

@@ -0,0 +1,24 @@
+#ifndef INC_6502_EMULATOR_OPCODE_HANDLER_DIRECTORY_H
+#define INC_6502_EMULATOR_OPCODE_HANDLER_DIRECTORY_H
+
+#include "../program.h"
+#include "opcode-handler.h"
+#include <unordered_map>
+#include <vector>
+#include <memory>
+
+using namespace std;
+
+class OpcodeHandlerDirectory {
+public:
+    explicit OpcodeHandlerDirectory(shared_ptr<Program> program, shared_ptr<RegisterManager> reg_man);
+
+    shared_ptr<OpcodeHandler> get_handler(uint8_t opcode);
+private:
+    unique_ptr<unordered_map<uint8_t, shared_ptr<OpcodeHandler>>> handlers;
+
+    void register_handler(shared_ptr<OpcodeHandler> handler);
+};
+
+
+#endif //INC_6502_EMULATOR_OPCODE_HANDLER_DIRECTORY_H

src/opcode/opcode-handler.cpp

@@ -0,0 +1,12 @@
+#include "../program.h"
+#include "opcode-handler.h"
+
+OpcodeHandler::OpcodeHandler(shared_ptr<Program> program, shared_ptr<RegisterManager> reg_man) {
+    this->program = program;
+    this->reg_man = reg_man;
+}
+
+void OpcodeHandler::move_program_counter(uint8_t forward_by) {
+    auto pc = reg_man->get_program_counter();
+    pc->set_value(pc->get_value() + forward_by);
+}

src/opcode/opcode-handler.h

@@ -0,0 +1,28 @@
+#ifndef INC_6502_EMULATOR_OPCODE_HANDLER_H
+#define INC_6502_EMULATOR_OPCODE_HANDLER_H
+
+#include "../program.h"
+#include "../register/register-manager.h"
+#include <vector>
+#include <memory>
+
+using namespace std;
+
+class OpcodeHandler {
+public:
+    OpcodeHandler(shared_ptr<Program> program, shared_ptr<RegisterManager> reg_man);
+
+    shared_ptr<vector<uint8_t>> get_handled_opcodes() { return handled_opcodes; }
+
+    virtual void execute() = 0;
+
+protected:
+    shared_ptr<vector<uint8_t>> handled_opcodes = make_shared<vector<uint8_t>>();
+    shared_ptr<Program> program;
+    shared_ptr<RegisterManager> reg_man;
+
+    void move_program_counter(uint8_t forward_by);
+};
+
+
+#endif //INC_6502_EMULATOR_OPCODE_HANDLER_H

src/program.cpp

@@ -0,0 +1,19 @@
+#include "program.h"
+
+#include <stdexcept>
+
+Program::Program(shared_ptr<vector<uint8_t>> bytes) {
+    this->bytes = bytes;
+}
+
+uint16_t Program::get_size() {
+    return bytes->size();
+}
+
+uint8_t Program::get_byte_at(uint16_t index) {
+    auto size = bytes->size();
+    if (size == 0 || bytes->size() - 1 < index)
+        throw runtime_error("Attempted to read past end of program");
+
+    return bytes->at(index);
+}

src/program.h

@@ -0,0 +1,21 @@
+#ifndef INC_6502_EMULATOR_PROGRAM_H
+#define INC_6502_EMULATOR_PROGRAM_H
+
+#include <memory>
+#include <vector>
+
+using namespace std;
+
+class Program {
+public:
+    explicit Program(shared_ptr<vector<uint8_t>> bytes);
+
+    uint8_t get_byte_at(uint16_t index);
+    uint16_t get_size();
+
+private:
+    shared_ptr<vector<uint8_t>> bytes;
+};
+
+
+#endif //INC_6502_EMULATOR_PROGRAM_H

src/register/register-manager.cpp

@@ -0,0 +1,39 @@
+#include "register-manager.h"
+#include "register.h"
+#include <memory>
+#include <cstring>
+
+using namespace std;
+
+RegisterManager::RegisterManager() {
+    accumulator = std::make_shared<Register<uint8_t>>(Register<uint8_t>("A"));
+    x_index = make_shared<Register<uint8_t>>(Register<uint8_t>("X"));
+    y_index = make_shared<Register<uint8_t>>(Register<uint8_t>("Y"));
+    stack_pointer = make_shared<Register<uint8_t>>(Register<uint8_t>("SP"));
+    status_register = make_shared<StatusRegister>(StatusRegister());
+    program_counter = make_shared<Register<uint16_t>>(Register<uint16_t>("PC"));
+}
+
+shared_ptr<Register<uint8_t>> RegisterManager::get_accumulator() {
+    return accumulator;
+}
+
+shared_ptr<Register<uint8_t>> RegisterManager::get_x_index() {
+    return x_index;
+}
+
+shared_ptr<Register<uint8_t>> RegisterManager::get_y_index() {
+    return y_index;
+}
+
+shared_ptr<Register<uint8_t>> RegisterManager::get_stack_pointer() {
+    return stack_pointer;
+}
+
+shared_ptr<StatusRegister> RegisterManager::get_status_register() {
+    return status_register;
+}
+
+shared_ptr<Register<uint16_t>> RegisterManager::get_program_counter() {
+    return program_counter;
+}

src/register/register-manager.h

@@ -0,0 +1,36 @@
+#ifndef INC_6502_EMULATOR_REGISTER_MANAGER_H
+#define INC_6502_EMULATOR_REGISTER_MANAGER_H
+
+#include "register.h"
+#include "status-register.h"
+#include <memory>
+
+using namespace std;
+
+class RegisterManager {
+public:
+    explicit RegisterManager();
+
+    shared_ptr<Register<uint8_t>> get_accumulator();
+
+    shared_ptr<Register<uint8_t>> get_x_index();
+
+    shared_ptr<Register<uint8_t>> get_y_index();
+
+    shared_ptr<Register<uint8_t>> get_stack_pointer();
+
+    shared_ptr<StatusRegister> get_status_register();
+
+    shared_ptr<Register<uint16_t>> get_program_counter();
+
+private:
+    shared_ptr<Register<uint8_t>> accumulator;
+    shared_ptr<Register<uint8_t>> x_index;
+    shared_ptr<Register<uint8_t>> y_index;
+    shared_ptr<Register<uint8_t>> stack_pointer;
+    shared_ptr<StatusRegister> status_register;
+    shared_ptr<Register<uint16_t>> program_counter;
+};
+
+
+#endif //INC_6502_EMULATOR_REGISTER_MANAGER_H

src/register/register.cpp

@@ -0,0 +1,30 @@
+#include "register.h"
+#include <stdexcept>
+#include <bitset>
+
+using namespace std;
+
+template<class T>
+Register<T>::Register(string name) {
+    this->name = name;
+    this->value = 0;
+}
+
+template<class T>
+string Register<T>::get_name() {
+    return name;
+}
+
+template<class T>
+T Register<T>::get_value() {
+    return value;
+}
+
+template<class T>
+void Register<T>::set_value(T value) {
+    this->value = value;
+}
+
+template class Register<uint8_t>;
+template class Register<uint16_t>;
+template class Register<bitset<8>>;

src/register/register.h

@@ -0,0 +1,28 @@
+#ifndef INC_6502_EMULATOR_REGISTER_H
+#define INC_6502_EMULATOR_REGISTER_H
+
+#include <cstdint>
+#include <string>
+
+using namespace std;
+
+template <class T>
+class Register
+{
+public:
+    explicit Register<T>(string name);
+
+    string get_name();
+
+    T get_value();
+    void set_value(T value);
+
+protected:
+    T value;
+
+private:
+    string name;
+};
+
+
+#endif //INC_6502_EMULATOR_REGISTER_H

src/register/status-register.cpp

@@ -0,0 +1,65 @@
+#include "status-register.h"
+
+const uint8_t CARRY_FLAG = 0;
+const uint8_t ZERO_FLAG = 1;
+const uint8_t INTERUPT_DISABLE_FLAG = 2;
+const uint8_t DECIMAL_FLAG = 3;
+const uint8_t BREAK_FLAG = 4;
+const uint8_t OVERFLOW_FLAG = 6;
+const uint8_t NEGATIVE_FLAG = 7;
+
+bool StatusRegister::is_carry_set() {
+    return this->value[CARRY_FLAG];
+}
+
+bool StatusRegister::is_zero_set() {
+    return this->value[ZERO_FLAG];
+}
+
+bool StatusRegister::is_interupt_disable_set() {
+    return this->value[INTERUPT_DISABLE_FLAG];
+}
+
+bool StatusRegister::is_decimal_set() {
+    return this->value[DECIMAL_FLAG];
+}
+
+bool StatusRegister::is_break_set() {
+    return this->value[BREAK_FLAG];
+}
+
+bool StatusRegister::is_overflow_set() {
+    return this->value[OVERFLOW_FLAG];
+}
+
+bool StatusRegister::is_negative_set() {
+    return this->value[NEGATIVE_FLAG];
+}
+
+void StatusRegister::set_carry(bool state) {
+    this->value[CARRY_FLAG] = state;
+}
+
+void StatusRegister::set_zero(bool state) {
+    this->value[ZERO_FLAG] = state;
+}
+
+void StatusRegister::set_interupt_disable(bool state) {
+    this->value[INTERUPT_DISABLE_FLAG] = state;
+}
+
+void StatusRegister::set_decimal(bool state) {
+    this->value[DECIMAL_FLAG] = state;
+}
+
+void StatusRegister::set_break(bool state) {
+    this->value[BREAK_FLAG] = state;
+}
+
+void StatusRegister::set_overflow(bool state) {
+    this->value[OVERFLOW_FLAG] = state;
+}
+
+void StatusRegister::set_negative(bool state) {
+    this->value[NEGATIVE_FLAG] = state;
+}

src/register/status-register.h

@@ -0,0 +1,29 @@
+#ifndef INC_6502_EMULATOR_STATUS_REGISTER_H
+#define INC_6502_EMULATOR_STATUS_REGISTER_H
+
+#include "register.h"
+#include <bitset>
+
+class StatusRegister : public Register<bitset<8>> {
+public:
+    explicit StatusRegister() : Register<bitset<8>>("P") {}
+
+    bool is_carry_set();
+    bool is_zero_set();
+    bool is_interupt_disable_set();
+    bool is_decimal_set();
+    bool is_break_set();
+    bool is_overflow_set();
+    bool is_negative_set();
+
+    void set_carry(bool state);
+    void set_zero(bool state);
+    void set_interupt_disable(bool state);
+    void set_decimal(bool state);
+    void set_break(bool state);
+    void set_overflow(bool state);
+    void set_negative(bool state);
+};
+
+
+#endif //INC_6502_EMULATOR_STATUS_REGISTER_H

test/flags-opcode-handler-test.cpp

@@ -0,0 +1,112 @@
+#include "gtest/gtest.h"
+#include "../src/machine.h"
+#include "../src/program.h"
+#include <memory>
+#include <vector>
+#include <sstream>
+#include <iostream>
+
+using namespace std;
+
+const uint8_t CLC = 0x18;
+const uint8_t SEC = 0x38;
+const uint8_t CLI = 0x58;
+const uint8_t SEI = 0x78;
+const uint8_t CLV = 0xB8;
+const uint8_t CLD = 0xD8;
+const uint8_t SED = 0xF8;
+
+unique_ptr<Machine> ft_get_machine(shared_ptr<vector<uint8_t>> code){
+    auto program = make_shared<Program>(Program(code));
+    auto machine = make_unique<Machine>(Machine(program));
+    return machine;
+}
+
+TEST(FlagOpcodeHandlerTest, ClearCarry) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{CLC});
+    auto machine = ft_get_machine(code);
+    auto status = machine->get_reg_man()->get_status_register();
+
+    ASSERT_EQ(0, status->is_carry_set());
+
+    status->set_carry(true);
+    ASSERT_EQ(1, status->is_carry_set());
+
+    machine->execute();
+    ASSERT_EQ(0, status->is_carry_set());
+}
+
+TEST(FlagOpcodeHandlerTest, SetCarry) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{SEC});
+    auto machine = ft_get_machine(code);
+    auto status = machine->get_reg_man()->get_status_register();
+
+    ASSERT_EQ(0, status->is_carry_set());
+
+    machine->execute();
+    ASSERT_EQ(1, status->is_carry_set());
+}
+
+TEST(FlagOpcodeHandlerTest, ClearInteruptDisable) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{CLI});
+    auto machine = ft_get_machine(code);
+    auto status = machine->get_reg_man()->get_status_register();
+
+    ASSERT_EQ(0, status->is_interupt_disable_set());
+
+    status->set_interupt_disable(true);
+    ASSERT_EQ(1, status->is_interupt_disable_set());
+
+    machine->execute();
+    ASSERT_EQ(0, status->is_interupt_disable_set());
+}
+
+TEST(FlagOpcodeHandlerTest, SetInteruptDisable) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{SEI});
+    auto machine = ft_get_machine(code);
+    auto status = machine->get_reg_man()->get_status_register();
+
+    ASSERT_EQ(0, status->is_interupt_disable_set());
+
+    machine->execute();
+    ASSERT_EQ(1, status->is_interupt_disable_set());
+}
+
+TEST(FlagOpcodeHandlerTest, ClearOverflow) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{CLV});
+    auto machine = ft_get_machine(code);
+    auto status = machine->get_reg_man()->get_status_register();
+
+    ASSERT_EQ(0, status->is_overflow_set());
+
+    status->set_overflow(true);
+    ASSERT_EQ(1, status->is_overflow_set());
+
+    machine->execute();
+    ASSERT_EQ(0, status->is_overflow_set());
+}
+
+TEST(FlagOpcodeHandlerTest, ClearDecimal) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{CLD});
+    auto machine = ft_get_machine(code);
+    auto status = machine->get_reg_man()->get_status_register();
+
+    ASSERT_EQ(0, status->is_decimal_set());
+
+    status->set_decimal(true);
+    ASSERT_EQ(1, status->is_decimal_set());
+
+    machine->execute();
+    ASSERT_EQ(0, status->is_decimal_set());
+}
+
+TEST(FlagOpcodeHandlerTest, SetDecimal) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{SED});
+    auto machine = ft_get_machine(code);
+    auto status = machine->get_reg_man()->get_status_register();
+
+    ASSERT_EQ(0, status->is_decimal_set());
+
+    machine->execute();
+    ASSERT_EQ(1, status->is_decimal_set());
+}

test/instruction-executor-test.cpp

@@ -0,0 +1,29 @@
+#include "gtest/gtest.h"
+#include "../src/program.h"
+#include "../src/instruction/instruction-executor.h"
+#include "../src/register/register-manager.h"
+#include "../src/opcode/opcode-handler-directory.h"
+#include <memory>
+#include <vector>
+#include <sstream>
+#include <iostream>
+
+using namespace std;
+
+const uint8_t CLC = 0x18;
+const uint8_t SEC = 0x38;
+
+const uint8_t LDX_IMMEDIATE = 0xA9;
+
+TEST(InstructionExecutor, Execute) {
+    auto reg_man = make_shared<RegisterManager>(RegisterManager());
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>
+            {SEC,
+             CLC
+            });
+    auto program = make_shared<Program>(Program(code));
+    auto opcode_handler_dir = make_shared<OpcodeHandlerDirectory>(OpcodeHandlerDirectory(program, reg_man));
+    auto executor = make_unique<InstructionExecutor>(InstructionExecutor(program, reg_man, opcode_handler_dir));
+
+    executor->execute();
+}

test/machine-test.cpp

@@ -0,0 +1,27 @@
+#include "gtest/gtest.h"
+#include "../src/machine.h"
+#include "../src/program.h"
+#include <memory>
+#include <vector>
+#include <sstream>
+#include <iostream>
+
+using namespace std;
+
+const uint8_t CLC = 0x18;
+const uint8_t SEC = 0x38;
+const uint8_t CLI = 0x58;
+const uint8_t SEI = 0x78;
+const uint8_t CLV = 0xB8;
+const uint8_t CLD = 0xD8;
+const uint8_t SED = 0xF8;
+
+const uint8_t LDX_IMMEDIATE = 0xA9;
+
+TEST(Machine, Execute) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{SEC, SEI, SED, CLI, CLV, CLD, CLC, LDX_IMMEDIATE, 0x6B});
+    auto program = make_shared<Program>(Program(code));
+    auto machine = make_unique<Machine>(Machine(program));
+
+    machine->execute();
+}

test/register-opcode-handler-test.cpp

@@ -0,0 +1,219 @@
+#include "gtest/gtest.h"
+#include "../src/machine.h"
+#include "../src/program.h"
+
+#include <memory>
+#include <vector>
+
+using namespace std;
+
+const uint8_t TAX = 0xAA;
+const uint8_t TXA = 0x8A;
+const uint8_t DEX = 0xCA;
+const uint8_t INX = 0xE8;
+const uint8_t TAY = 0xA8;
+const uint8_t TYA = 0x98;
+const uint8_t DEY = 0x88;
+const uint8_t INY = 0xC8;
+
+unique_ptr<Machine> rt_get_machine(shared_ptr<vector<uint8_t>> code) {
+    auto program = make_shared<Program>(Program(code));
+    auto machine = make_unique<Machine>(Machine(program));
+    return machine;
+}
+
+TEST(RegisterOpcodeHandler, TransferAtoX) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{TAX});
+    auto machine = rt_get_machine(code);
+    auto reg_man = machine->get_reg_man();
+
+    auto aval = reg_man->get_accumulator()->get_value();
+    auto xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0, aval);
+    ASSERT_EQ(0, xval);
+
+    machine->execute();
+    aval = reg_man->get_accumulator()->get_value();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0, aval);
+    ASSERT_EQ(0, xval);
+
+    reg_man->get_program_counter()->set_value(0);
+    reg_man->get_accumulator()->set_value(0x3e);
+    machine->execute();
+    aval = reg_man->get_accumulator()->get_value();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0x3e, aval);
+    ASSERT_EQ(0x3e, xval);
+}
+
+TEST(RegisterOpcodeHandler, TransferXtoA) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{TXA});
+    auto machine = rt_get_machine(code);
+    auto reg_man = machine->get_reg_man();
+
+    auto aval = reg_man->get_accumulator()->get_value();
+    auto xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0, aval);
+    ASSERT_EQ(0, xval);
+
+    machine->execute();
+    aval = reg_man->get_accumulator()->get_value();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0, aval);
+    ASSERT_EQ(0, xval);
+
+    reg_man->get_program_counter()->set_value(0);
+    reg_man->get_x_index()->set_value(0x4f);
+    machine->execute();
+    aval = reg_man->get_accumulator()->get_value();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0x4f, aval);
+    ASSERT_EQ(0x4f, xval);
+}
+
+TEST(RegisterOpcodeHandler, DecrementX) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{DEX});
+    auto machine = rt_get_machine(code);
+    auto reg_man = machine->get_reg_man();
+
+    auto xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0, xval);
+
+    machine->execute();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0xff, xval);
+
+    reg_man->get_program_counter()->set_value(0);
+    machine->execute();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0xfe, xval);
+
+    reg_man->get_program_counter()->set_value(0);
+    reg_man->get_x_index()->set_value(0x45);
+    machine->execute();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0x44, xval);
+}
+
+TEST(RegisterOpcodeHandler, IncrementX) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{INX});
+    auto machine = rt_get_machine(code);
+    auto reg_man = machine->get_reg_man();
+
+    auto xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0, xval);
+
+    machine->execute();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0x01, xval);
+
+    reg_man->get_program_counter()->set_value(0);
+    machine->execute();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0x02, xval);
+
+    reg_man->get_program_counter()->set_value(0);
+    reg_man->get_x_index()->set_value(0x45);
+    machine->execute();
+    xval = reg_man->get_x_index()->get_value();
+    ASSERT_EQ(0x46, xval);
+}
+
+TEST(RegisterOpcodeHandler, TransferAtoY) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{TAY});
+    auto machine = rt_get_machine(code);
+    auto reg_man = machine->get_reg_man();
+
+    auto aval = reg_man->get_accumulator()->get_value();
+    auto yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0, aval);
+    ASSERT_EQ(0, yval);
+
+    machine->execute();
+    aval = reg_man->get_accumulator()->get_value();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0, aval);
+    ASSERT_EQ(0, yval);
+
+    reg_man->get_program_counter()->set_value(0);
+    reg_man->get_accumulator()->set_value(0xaf);
+    machine->execute();
+    aval = reg_man->get_accumulator()->get_value();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0xaf, aval);
+    ASSERT_EQ(0xaf, yval);
+}
+
+TEST(RegisterOpcodeHandler, TransferYtoA) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{TYA});
+    auto machine = rt_get_machine(code);
+    auto reg_man = machine->get_reg_man();
+
+    auto aval = reg_man->get_accumulator()->get_value();
+    auto yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0, aval);
+    ASSERT_EQ(0, yval);
+
+    machine->execute();
+    aval = reg_man->get_accumulator()->get_value();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0, aval);
+    ASSERT_EQ(0, yval);
+
+    reg_man->get_program_counter()->set_value(0);
+    reg_man->get_y_index()->set_value(0xff);
+    machine->execute();
+    aval = reg_man->get_accumulator()->get_value();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0xff, aval);
+    ASSERT_EQ(0xff, yval);
+}
+
+TEST(RegisterOpcodeHandler, DecrementY) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{DEY});
+    auto machine = rt_get_machine(code);
+    auto reg_man = machine->get_reg_man();
+
+    auto yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0, yval);
+
+    machine->execute();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0xff, yval);
+
+    reg_man->get_program_counter()->set_value(0);
+    machine->execute();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0xfe, yval);
+
+    reg_man->get_program_counter()->set_value(0);
+    reg_man->get_y_index()->set_value(0x3b);
+    machine->execute();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0x3a, yval);
+}
+
+TEST(RegisterOpcodeHandler, IncrementY) {
+    auto code = make_shared<vector<uint8_t>>(vector<uint8_t>{INY});
+    auto machine = rt_get_machine(code);
+    auto reg_man = machine->get_reg_man();
+
+    auto yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0, yval);
+
+    machine->execute();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0x01, yval);
+
+    reg_man->get_program_counter()->set_value(0);
+    machine->execute();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0x02, yval);
+
+    reg_man->get_program_counter()->set_value(0);
+    reg_man->get_y_index()->set_value(0x3b);
+    machine->execute();
+    yval = reg_man->get_y_index()->get_value();
+    ASSERT_EQ(0x3c, yval);
+}

test/register-test.cpp

@@ -0,0 +1,8 @@
+#include "gtest/gtest.h"
+#include "../src/register/register.h"
+
+TEST(Construct, Equals) {
+    auto reg = new Register<uint16_t>("PC");
+
+    EXPECT_EQ("PC", reg->get_name());
+}

test/status-register-test.cpp

@@ -0,0 +1,170 @@
+#include "gtest/gtest.h"
+#include "../src/register/status-register.h"
+#include <memory>
+#include <sstream>
+#include <iostream>
+
+using namespace std;
+
+string get_bit_pattern(StatusRegister* reg) {
+    stringstream stream;
+    stream << reg->get_value();
+
+    return stream.str();
+}
+
+TEST(StatusRegister, Construct) {
+    auto reg = make_unique<StatusRegister>(StatusRegister());
+    auto bit_pattern = get_bit_pattern(reg.get());
+
+    EXPECT_EQ("P", reg->get_name());
+
+    EXPECT_EQ("00000000", bit_pattern);
+
+    EXPECT_EQ(false, reg->is_carry_set());
+    EXPECT_EQ(false, reg->is_zero_set());
+    EXPECT_EQ(false, reg->is_interupt_disable_set());
+    EXPECT_EQ(false, reg->is_decimal_set());
+    EXPECT_EQ(false, reg->is_break_set());
+    EXPECT_EQ(false, reg->is_overflow_set());
+    EXPECT_EQ(false, reg->is_negative_set());
+}
+
+TEST(StatusRegister, CarryFlag) {
+    auto reg = make_unique<StatusRegister>(StatusRegister());
+    EXPECT_EQ(false, reg->is_carry_set());
+
+    reg->set_carry(true);
+    EXPECT_EQ(true, reg->is_carry_set());
+
+    auto bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000001", bit_pattern);
+
+    reg->set_carry(false);
+    EXPECT_EQ(false, reg->is_carry_set());
+    bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000000", bit_pattern);
+}
+
+TEST(StatusRegister, ZeroFlag) {
+    auto reg = make_unique<StatusRegister>(StatusRegister());
+    EXPECT_EQ(false, reg->is_zero_set());
+
+    reg->set_zero(true);
+    EXPECT_EQ(true, reg->is_zero_set());
+
+    auto bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000010", bit_pattern);
+
+    reg->set_zero(false);
+    EXPECT_EQ(false, reg->is_zero_set());
+    bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000000", bit_pattern);
+}
+
+TEST(StatusRegister, InteruptDisableFlag) {
+    auto reg = make_unique<StatusRegister>(StatusRegister());
+    EXPECT_EQ(false, reg->is_interupt_disable_set());
+
+    reg->set_interupt_disable(true);
+    EXPECT_EQ(true, reg->is_interupt_disable_set());
+
+    auto bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000100", bit_pattern);
+
+    reg->set_interupt_disable(false);
+    EXPECT_EQ(false, reg->is_interupt_disable_set());
+    bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000000", bit_pattern);
+}
+
+TEST(StatusRegister, DecimalFlag) {
+    auto reg = make_unique<StatusRegister>(StatusRegister());
+    EXPECT_EQ(false, reg->is_decimal_set());
+
+    reg->set_decimal(true);
+    EXPECT_EQ(true, reg->is_decimal_set());
+
+    auto bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00001000", bit_pattern);
+
+    reg->set_decimal(false);
+    EXPECT_EQ(false, reg->is_decimal_set());
+    bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000000", bit_pattern);
+}
+
+TEST(StatusRegister, BreakFlag) {
+    auto reg = make_unique<StatusRegister>(StatusRegister());
+    EXPECT_EQ(false, reg->is_break_set());
+
+    reg->set_break(true);
+    EXPECT_EQ(true, reg->is_break_set());
+
+    auto bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00010000", bit_pattern);
+
+    reg->set_break(false);
+    EXPECT_EQ(false, reg->is_break_set());
+    bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000000", bit_pattern);
+}
+
+TEST(StatusRegister, OverflowFlag) {
+    auto reg = make_unique<StatusRegister>(StatusRegister());
+    EXPECT_EQ(false, reg->is_overflow_set());
+
+    reg->set_overflow(true);
+    EXPECT_EQ(true, reg->is_overflow_set());
+
+    auto bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("01000000", bit_pattern);
+
+    reg->set_overflow(false);
+    EXPECT_EQ(false, reg->is_overflow_set());
+    bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000000", bit_pattern);
+}
+
+TEST(StatusRegister, NegativeFlag) {
+    auto reg = make_unique<StatusRegister>(StatusRegister());
+    EXPECT_EQ(false, reg->is_negative_set());
+
+    reg->set_negative(true);
+    EXPECT_EQ(true, reg->is_negative_set());
+
+    auto bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("10000000", bit_pattern);
+
+    reg->set_negative(false);
+    EXPECT_EQ(false, reg->is_negative_set());
+    bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000000", bit_pattern);
+}
+
+TEST(StatusRegister, AllFlags) {
+    auto reg = make_unique<StatusRegister>(StatusRegister());
+    EXPECT_EQ(false, reg->is_negative_set());
+
+    reg->set_carry(true);
+    reg->set_zero(true);
+    reg->set_interupt_disable(true);
+    reg->set_decimal(true);
+    reg->set_break(true);
+    reg->set_overflow(true);
+    reg->set_negative(true);
+
+    auto bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("11011111", bit_pattern);
+
+    reg->set_carry(false);
+    reg->set_zero(false);
+    reg->set_interupt_disable(false);
+    reg->set_decimal(false);
+    reg->set_break(false);
+    reg->set_overflow(false);
+    reg->set_negative(false);
+
+    bit_pattern = get_bit_pattern(reg.get());
+    EXPECT_EQ("00000000", bit_pattern);
+}