diff --git a/Chapter05/build.rs b/Chapter05/build.rs
index 3ef607f..1208988 100644
--- a/Chapter05/build.rs
+++ b/Chapter05/build.rs
@@ -11,14 +11,12 @@ fn main() {
     Command::new("ar").args(&["crus", "libmotor1.a", "motor1.o"])
                       .current_dir(&Path::new(&out_dir))
                       .status().unwrap();
-
     Command::new("gcc").args(&["src/motor2.c", "-c", "-fPIC", "-o"])
                        .arg(&format!("{}/motor2.o", out_dir))
                        .status().unwrap();
     Command::new("ar").args(&["crus", "libmotor2.a", "motor2.o"])
                       .current_dir(&Path::new(&out_dir))
                       .status().unwrap();
-
     Command::new("gcc").args(&["src/motor3.c", "-c", "-fPIC", "-o"])
                        .arg(&format!("{}/motor3.o", out_dir))
                        .status().unwrap();
@@ -26,8 +24,30 @@ fn main() {
                       .current_dir(&Path::new(&out_dir))
                       .status().unwrap();
 
+    Command::new("gcc").args(&["src/elevator1.c", "-c", "-fPIC", "-o"])
+                       .arg(&format!("{}/elevator1.o", out_dir))
+                       .status().unwrap();
+    Command::new("ar").args(&["crus", "libelevator1.a", "elevator1.o"])
+                      .current_dir(&Path::new(&out_dir))
+                      .status().unwrap();
+    Command::new("gcc").args(&["src/elevator2.c", "-c", "-fPIC", "-o"])
+                       .arg(&format!("{}/elevator2.o", out_dir))
+                       .status().unwrap();
+    Command::new("ar").args(&["crus", "libelevator2.a", "elevator2.o"])
+                      .current_dir(&Path::new(&out_dir))
+                      .status().unwrap();
+    Command::new("gcc").args(&["src/elevator3.c", "-c", "-fPIC", "-o"])
+                       .arg(&format!("{}/elevator3.o", out_dir))
+                       .status().unwrap();
+    Command::new("ar").args(&["crus", "libelevator3.a", "elevator3.o"])
+                      .current_dir(&Path::new(&out_dir))
+                      .status().unwrap();
+
     println!("cargo:rustc-link-search=native={}", out_dir);
     println!("cargo:rustc-link-lib=static=motor1");
     println!("cargo:rustc-link-lib=static=motor2");
     println!("cargo:rustc-link-lib=static=motor3");
+    println!("cargo:rustc-link-lib=static=elevator1");
+    println!("cargo:rustc-link-lib=static=elevator2");
+    println!("cargo:rustc-link-lib=static=elevator3");
 }
diff --git a/Chapter05/src/elevator1.c b/Chapter05/src/elevator1.c
new file mode 100644
index 0000000..f2f0ccb
--- /dev/null
+++ b/Chapter05/src/elevator1.c
@@ -0,0 +1,6 @@
+
+int elevator1_poll_floor_request()
+{
+   //real implementation would interface with hardware here
+   return 0;
+}
diff --git a/Chapter05/src/elevator2.c b/Chapter05/src/elevator2.c
new file mode 100644
index 0000000..f2f0ccb
--- /dev/null
+++ b/Chapter05/src/elevator2.c
@@ -0,0 +1,6 @@
+
+int elevator1_poll_floor_request()
+{
+   //real implementation would interface with hardware here
+   return 0;
+}
diff --git a/Chapter05/src/elevator3.c b/Chapter05/src/elevator3.c
new file mode 100644
index 0000000..f2f0ccb
--- /dev/null
+++ b/Chapter05/src/elevator3.c
@@ -0,0 +1,6 @@
+
+int elevator1_poll_floor_request()
+{
+   //real implementation would interface with hardware here
+   return 0;
+}
diff --git a/Chapter05/src/elevator_drivers.rs b/Chapter05/src/elevator_drivers.rs
index e69de29..3fb8c97 100644
--- a/Chapter05/src/elevator_drivers.rs
+++ b/Chapter05/src/elevator_drivers.rs
@@ -0,0 +1,69 @@
+use libc::c_int;
+
+#[link(name = "elevator1")]
+extern {
+   pub fn elevator1_poll_floor_request() -> c_int;
+}
+
+#[link(name = "elevator2")]
+extern {
+   pub fn elevator2_poll_floor_request() -> c_int;
+}
+
+#[link(name = "elevator3")]
+extern {
+   pub fn elevator3_poll_floor_request() -> c_int;
+}
+
+pub trait ElevatorDriver
+{
+   fn poll_floor_request(&self) -> Option<u64>;
+}
+
+pub struct ElevatorDriver1;
+impl ElevatorDriver for ElevatorDriver1
+{
+   fn poll_floor_request(&self) -> Option<u64>
+   {
+      unsafe {
+         let req = elevator1_poll_floor_request();
+         if req > 0 {
+            Some(req as u64)
+         } else {
+            None
+         }
+      }
+   }
+}
+
+pub struct ElevatorDriver2;
+impl ElevatorDriver for ElevatorDriver2
+{
+   fn poll_floor_request(&self) -> Option<u64>
+   {
+      unsafe {
+         let req = elevator2_poll_floor_request();
+         if req > 0 {
+            Some(req as u64)
+         } else {
+            None
+         }
+      }
+   }
+}
+
+pub struct ElevatorDriver3;
+impl ElevatorDriver for ElevatorDriver3
+{
+   fn poll_floor_request(&self) -> Option<u64>
+   {
+      unsafe {
+         let req = elevator3_poll_floor_request();
+         if req > 0 {
+            Some(req as u64)
+         } else {
+            None
+         }
+      }
+   }
+}
diff --git a/Chapter05/src/motor_controllers.rs b/Chapter05/src/motor_controllers.rs
index c107f13..c62189d 100644
--- a/Chapter05/src/motor_controllers.rs
+++ b/Chapter05/src/motor_controllers.rs
@@ -25,13 +25,13 @@ pub enum MotorInput
 
 pub trait MotorDriver
 {
-   fn adjust_motor(input: MotorInput);
+   fn adjust_motor(&self, input: MotorInput);
 }
 
 struct Motor1;
 impl MotorDriver for Motor1
 {
-   fn adjust_motor(input: MotorInput)
+   fn adjust_motor(&self, input: MotorInput)
    {
       if let MotorInput::Motor1 { target_force: target_force } = input {
          unsafe {
@@ -44,9 +44,9 @@ impl MotorDriver for Motor1
 struct Motor2;
 impl MotorDriver for Motor2
 {
-   fn adjust_motor(input: MotorInput)
+   fn adjust_motor(&self, input: MotorInput)
    {
-      if let MotorInput::Motor1 { target_force: target_force } = input {
+      if let MotorInput::Motor2 { target_force: target_force } = input {
          unsafe {
             motor2_adjust_motor(target_force);
          }
@@ -57,12 +57,90 @@ impl MotorDriver for Motor2
 struct Motor3;
 impl MotorDriver for Motor3
 {
-   fn adjust_motor(input: MotorInput)
+   fn adjust_motor(&self, input: MotorInput)
    {
-      if let MotorInput::Motor1 { target_force: target_force } = input {
+      if let MotorInput::Motor3 { target_force: target_force } = input {
          unsafe {
             motor3_adjust_motor(target_force);
          }
       }
    }
 }
+
+pub trait MotorController
+{
+   fn adjust_motor(&self, f: f64);
+   fn max_force(&self) -> f64;
+}
+
+pub struct MotorController1
+{
+   motor: Motor1
+}
+pub fn newMotorController1() -> Box<MotorController>
+{
+   Box::new(MotorController1 {
+      motor: Motor1
+   })
+}
+impl MotorController for MotorController1
+{
+   fn adjust_motor(&self, f: f64)
+   {
+      self.motor.adjust_motor(MotorInput::Motor1 {
+         target_force: f
+      })
+   }
+   fn max_force(&self) -> f64
+   {
+      50000.0
+   }
+}
+
+pub struct MotorController2
+{
+   motor: Motor2
+}
+pub fn newMotorController2() -> Box<MotorController>
+{
+   Box::new(MotorController2 {
+      motor: Motor2
+   })
+}
+impl MotorController for MotorController2
+{
+   fn adjust_motor(&self, f: f64)
+   {
+      self.motor.adjust_motor(MotorInput::Motor2 {
+         target_force: f
+      })
+   }
+   fn max_force(&self) -> f64
+   {
+      100000.0
+   }
+}
+
+pub struct MotorController3
+{
+   motor: Motor3
+}
+pub fn newMotorController3() -> Box<MotorController>
+{
+   Box::new(MotorController3 {
+      motor: Motor3
+   })
+}
+impl MotorController for MotorController3
+{
+   fn adjust_motor(&self, f: f64)
+   {
+      self.motor.adjust_motor(MotorInput::Motor3 {
+         target_force: f
+      })
+   }
+   fn max_force(&self) -> f64
+   {
+      90000.0
+   }
+}