diff --git a/src/components/cpu/intel_4004.rs b/src/components/cpu/intel_4004.rs
index 32c093d..87dc456 100644
--- a/src/components/cpu/intel_4004.rs
+++ b/src/components/cpu/intel_4004.rs
@@ -26,7 +26,7 @@ pub struct Intel4004 {
     accumulator: u8,
     carry: bool,
     index_registers: [u8; 16],
-    program_counter: U12,
+    pub(crate) program_counter: U12,
     stack: [U12; 3],
     stack_pointer: u8,
     cycle_count: u64,
diff --git a/src/components/cpu/mos_6502.rs b/src/components/cpu/mos_6502.rs
index 405a479..35fef5b 100644
--- a/src/components/cpu/mos_6502.rs
+++ b/src/components/cpu/mos_6502.rs
@@ -101,7 +101,7 @@ impl MOS6502 {
         }
     }
 
-    fn read_data_bus(&self) -> u8 {
+    fn _read_data_bus(&self) -> u8 {
         let mut data = 0;
 
         for i in 0..8 {
diff --git a/src/components/memory/intel_4001.rs b/src/components/memory/intel_4001.rs
index 5a89b23..e6b21a8 100644
--- a/src/components/memory/intel_4001.rs
+++ b/src/components/memory/intel_4001.rs
@@ -352,11 +352,11 @@ impl Intel4001 {
         self.input_latch
     }
 
-    pub fn get_io_mode(&self) -> IoMode {
+    fn get_io_mode(&self) -> IoMode {
         self.io_mode
     }
 
-    pub fn set_io_mode(&mut self, mode: IoMode) {
+    fn set_io_mode(&mut self, mode: IoMode) {
         self.io_mode = mode;
         match mode {
             IoMode::Input => self.tri_state_io_pins(),
diff --git a/src/lib.rs b/src/lib.rs
index 9e6567a..77621ba 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,7 +4,7 @@ pub mod connection;
 pub mod components;
 pub mod systems;
 mod bus;
-mod types;
+pub mod types;
 
 // Re-export commonly used items for easier importing
 pub use component::{Component, BaseComponent};
diff --git a/src/main.rs b/src/main.rs
index 3c0b649..90bb9be 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,4 @@
+use rusty_emu::types::U12;
 use rusty_emu::systems::intel_mcs_4::IntelMcs4;
 use std::thread;
 use std::time::{Duration, Instant};
@@ -40,7 +41,7 @@ fn main() {
     }
 
     // Set starting program counter
-    if let Err(e) = mcs4.set_cpu_program_counter(0x000) {
+    if let Err(e) = mcs4.set_cpu_program_counter(U12::from(0x000)) {
         eprintln!("Failed to set program counter: {}", e);
         return;
     }
@@ -58,7 +59,7 @@ fn main() {
     println!();
 
     // Run the Fibonacci demo
-    run_fibonacci_demo(&mut mcs4);
+    run_fibonacci_demo(mcs4);
 }
 
 fn compile_fibonacci_program() -> Vec<u8> {
@@ -74,7 +75,7 @@ fn compile_fibonacci_program() -> Vec<u8> {
     ]
 }
 
-fn run_fibonacci_demo(mcs4: &mut IntelMcs4) {
+fn run_fibonacci_demo(mcs4: IntelMcs4) {
     let start_time = Instant::now();
 
     println!("Cycle | Fibonacci | Accumulator | PC");
diff --git a/src/systems/intel_mcs_4.rs b/src/systems/intel_mcs_4.rs
index c78002a..3215ccb 100644
--- a/src/systems/intel_mcs_4.rs
+++ b/src/systems/intel_mcs_4.rs
@@ -9,6 +9,7 @@ use crate::component::Component;
 use crate::components::memory::intel_4001::Intel4001;
 use crate::components::memory::intel_4002::Intel4002;
 use crate::pin::Pin;
+use crate::types::U12;
 
 pub struct IntelMcs4 {
     components: HashMap<String, Arc<Mutex<dyn Component>>>,
@@ -146,50 +147,43 @@ impl IntelMcs4 {
 
         Err("RAM component not found".to_string())
     }
-
-    pub fn set_cpu_program_counter(&mut self, address: u16) -> Result<(), String> {
-        if let Some(cpu_component) = self.components.get("cpu") {
-            if let Ok(mut cpu) = cpu_component.lock() {
-                // Downcast to Intel4004
-                if let Some(cpu_ref) = cpu.as_any_mut().downcast_mut::<Intel4004>() {
-                    cpu_ref.set_program_counter(address);
-                    return Ok(());
-                }
+    pub fn set_cpu_program_counter(&mut self, address: U12) -> Result<(), String> {
+        if let Some(cpu_component) = self.components.get_mut("cpu") {
+            if let Some(cpu) = cpu_component.as_any_mut().downcast_mut::<Intel4004>() {
+                cpu.program_counter = address;
+                Ok(())
+            } else {
+                Err("CPU component is not of type Intel 4004".to_string())
             }
+        } else {
+            Err("CPU component not found".to_string())
         }
-
-        Err("CPU component not found".to_string())
     }
-
     pub fn get_cpu_state(&self) -> Result<CpuState, String> {
         if let Some(cpu_component) = self.components.get("cpu") {
-            if let Ok(cpu) = cpu_component.lock() {
-                if let Some(cpu_ref) = cpu.as_any().downcast_ref::<Intel4004>() {
-                    return Ok(CpuState {
-                        program_counter: cpu_ref.get_program_counter(),
-                        accumulator: cpu_ref.get_accumulator(),
-                        carry: cpu_ref.get_carry(),
-                        stack_pointer: cpu_ref.get_stack_pointer(),
-                        cycle_count: cpu_ref.get_cycle_count(),
-                    });
-                }
+            if let Some(cpu) = cpu_component.as_any().downcast_ref::<Intel4004>() {
+                return Ok(CpuState {
+                    program_counter: cpu.get_program_counter(),
+                    accumulator: cpu.get_accumulator(),
+                    carry: cpu.get_carry(),
+                    stack_pointer: cpu.get_stack_pointer(),
+                    cycle_count: cpu.get_cycle_count(),
+                });
+            } else {
+                Err("CPU component is not of type Intel 4004".to_string())
             }
+        } else {
+            Err("CPU component not found".to_string())
         }
-
-        Err("CPU component not found".to_string())
     }
-
     pub fn reset_system(&mut self) {
         println!("Resetting MCS-4 system...");
-        if let Some(cpu_component) = self.components.get("cpu") {
-            if let Ok(mut cpu) = cpu_component.lock() {
-                if let Some(cpu_ref) = cpu.as_any_mut().downcast_mut::<Intel4004>() {
-                    cpu_ref.reset();
-                }
+        if let Some(cpu_component) = self.components.get_mut("cpu") {
+            if let Some(cpu) = cpu_component.as_any_mut().downcast_mut::<Intel4004>() {
+                    cpu.reset();
             }
         }
     }
-
     pub fn get_system_info(&self) -> SystemInfo {
         SystemInfo {
             cpu_speed: 750_000.0,