diff --git a/src/calculate/pass_4.rs b/src/calculate/pass_4.rs
index 9cc5723..2866e6b 100644
--- a/src/calculate/pass_4.rs
+++ b/src/calculate/pass_4.rs
@@ -1,114 +1,50 @@
-use super::item::{Attribute, EffectCategory};
+use super::item::Attribute;
 use super::{Info, Pass, Ship};
 
 pub struct PassFour {}
 
-fn add_attribute(ship: &mut Ship, attribute_id: i32, base_value: f64, value: f64) {
-    let mut attribute = Attribute::new(base_value);
-    attribute.value = Some(value);
-    ship.hull.attributes.insert(attribute_id, attribute);
-}
-
-fn calculate_align_time(ship: &mut Ship) -> (f64, f64) {
-    /* Align-time is based on agility (70) and mass (4). */
-
-    let base_agility = ship.hull.attributes.get(&70).unwrap().base_value;
-    let base_mass = ship.hull.attributes.get(&4).unwrap().base_value;
-    let base_align_time = -(0.25 as f64).ln() * base_agility * base_mass / 1000000.0;
-
-    let agility = ship.hull.attributes.get(&70).unwrap().value.unwrap();
-    let mass = ship.hull.attributes.get(&4).unwrap().value.unwrap();
-    let align_time = -(0.25 as f64).ln() * agility * mass / 1000000.0;
-
-    (base_align_time, align_time)
-}
-
-fn add_scan_strength(ship: &mut Ship) -> (f64, f64) {
-    /* Scan Strength can be one of 4 values. */
-
-    let mut base_scan_strength = 0.0;
-    let mut scan_strength = 0.0;
-    for attribute_id in vec![208, 209, 210, 211].iter() {
-        if ship.hull.attributes.contains_key(attribute_id) {
-            let attribute = ship.hull.attributes.get(attribute_id).unwrap();
-
-            if attribute.base_value > base_scan_strength {
-                base_scan_strength = attribute.base_value;
-            }
-            if attribute.value.unwrap() > scan_strength {
-                scan_strength = attribute.value.unwrap();
-            }
-        }
+mod align_time;
+mod cpu_power;
+mod scan_strength;
+
+#[allow(non_camel_case_types)]
+pub enum AttributeId {
+    alignTime = -1,
+    scanStrength = -2,
+    cpuUsed = -3,
+    powerUsed = -4,
+    cpuUnused = -5,
+    powerUnused = -6,
+
+    mass = 4,
+    powerOutput = 11,
+    power = 30,
+    cpuOutput = 48,
+    cpu = 50,
+    agility = 70,
+
+    scanRadarStrength = 208,
+    scanLadarStrength = 209,
+    scanMagnetometricStrength = 210,
+    scanGravimetricStrength = 211,
+}
+
+impl Ship {
+    pub fn add_attribute(&mut self, attribute_id: AttributeId, base_value: f64, value: f64) {
+        let mut attribute = Attribute::new(base_value);
+        attribute.value = Some(value);
+        self.hull.attributes.insert(attribute_id as i32, attribute);
     }
-
-    (base_scan_strength, scan_strength)
-}
-
-fn add_cpu_used(ship: &mut Ship) -> (f64, f64) {
-    /* How much CPU is being used, which is adding up cpuOuput (50) from all items. */
-
-    let mut cpu_used = 0.0;
-    for item in &ship.items {
-        if item.attributes.contains_key(&50) && item.state != EffectCategory::Passive {
-            cpu_used += item.attributes.get(&50).unwrap().value.unwrap();
-        }
-    }
-
-    (0.0, cpu_used)
-}
-
-fn add_pg_used(ship: &mut Ship) -> (f64, f64) {
-    /* How much PG is being used, which is adding up powerOutput (30) from all items. */
-
-    let mut pg_used = 0.0;
-    for item in &ship.items {
-        if item.attributes.contains_key(&30) && item.state != EffectCategory::Passive {
-            pg_used += item.attributes.get(&30).unwrap().value.unwrap();
-        }
-    }
-
-    (0.0, pg_used)
-}
-
-fn add_cpu_unused(ship: &mut Ship) -> (f64, f64) {
-    /* How much CPU is left, which is the total CPU minus the usage. */
-
-    let cpu_used = ship.hull.attributes.get(&-3).unwrap().value.unwrap();
-    let cpu_output = ship.hull.attributes.get(&48).unwrap().value.unwrap();
-    let cpu_unused = cpu_output - cpu_used;
-
-    (0.0, cpu_unused)
-}
-
-fn add_pg_unused(ship: &mut Ship) -> (f64, f64) {
-    /* How much PG is left, which is the total PG minus the usage. */
-
-    let pg_used = ship.hull.attributes.get(&-4).unwrap().value.unwrap();
-    let pg_output = ship.hull.attributes.get(&11).unwrap().value.unwrap();
-    let pg_unused = pg_output - pg_used;
-
-    (0.0, pg_unused)
 }
 
 /* Attributes don't contain all information displayed, so we calculate some fake attributes with those values. */
 impl Pass for PassFour {
     fn pass(_info: &Info, ship: &mut Ship) {
-        let align_time = calculate_align_time(ship);
-        add_attribute(ship, -1, align_time.0, align_time.1);
-
-        let scan_strength = add_scan_strength(ship);
-        add_attribute(ship, -2, scan_strength.0, scan_strength.1);
-
-        let cpu_used = add_cpu_used(ship);
-        add_attribute(ship, -3, cpu_used.0, cpu_used.1);
-
-        let pg_used = add_pg_used(ship);
-        add_attribute(ship, -4, pg_used.0, pg_used.1);
-
-        let cpu_unused = add_cpu_unused(ship);
-        add_attribute(ship, -5, cpu_unused.0, cpu_unused.1);
-
-        let pg_unused = add_pg_unused(ship);
-        add_attribute(ship, -6, pg_unused.0, pg_unused.1);
+        align_time::attribute_align_time(ship);
+        scan_strength::attribute_scan_strength(ship);
+        cpu_power::attribute_cpu_used(ship);
+        cpu_power::attribute_power_used(ship);
+        cpu_power::attribute_cpu_unused(ship);
+        cpu_power::attribute_power_unused(ship);
     }
 }
diff --git a/src/calculate/pass_4/align_time.rs b/src/calculate/pass_4/align_time.rs
new file mode 100644
index 0000000..2a4bc1e
--- /dev/null
+++ b/src/calculate/pass_4/align_time.rs
@@ -0,0 +1,25 @@
+use super::super::Ship;
+use super::AttributeId;
+
+pub fn attribute_align_time(ship: &mut Ship) {
+    /* Align-time is based on agility and mass. */
+
+    let attr_agility = AttributeId::agility as i32;
+    let attr_mass = AttributeId::mass as i32;
+
+    let base_agility = ship.hull.attributes.get(&attr_agility).unwrap().base_value;
+    let base_mass = ship.hull.attributes.get(&attr_mass).unwrap().base_value;
+    let base_align_time = -(0.25 as f64).ln() * base_agility * base_mass / 1000000.0;
+
+    let agility = ship
+        .hull
+        .attributes
+        .get(&attr_agility)
+        .unwrap()
+        .value
+        .unwrap();
+    let mass = ship.hull.attributes.get(&attr_mass).unwrap().value.unwrap();
+    let align_time = -(0.25 as f64).ln() * agility * mass / 1000000.0;
+
+    ship.add_attribute(AttributeId::alignTime, base_align_time, align_time);
+}
diff --git a/src/calculate/pass_4/cpu_power.rs b/src/calculate/pass_4/cpu_power.rs
new file mode 100644
index 0000000..83f0ea8
--- /dev/null
+++ b/src/calculate/pass_4/cpu_power.rs
@@ -0,0 +1,83 @@
+use super::super::item::EffectCategory;
+use super::super::Ship;
+use super::AttributeId;
+
+pub fn attribute_cpu_used(ship: &mut Ship) {
+    /* How much CPU is being used, which is adding up cpu from all items. */
+
+    let attr_cpu = AttributeId::cpu as i32;
+
+    let mut cpu_used = 0.0;
+    for item in &ship.items {
+        if item.attributes.contains_key(&attr_cpu) && item.state != EffectCategory::Passive {
+            cpu_used += item.attributes.get(&attr_cpu).unwrap().value.unwrap();
+        }
+    }
+
+    ship.add_attribute(AttributeId::cpuUsed, 0.0, cpu_used);
+}
+
+pub fn attribute_power_used(ship: &mut Ship) {
+    /* How much PG is being used, which is adding up power from all items. */
+
+    let attr_power = AttributeId::power as i32;
+
+    let mut power_used = 0.0;
+    for item in &ship.items {
+        if item.attributes.contains_key(&attr_power) && item.state != EffectCategory::Passive {
+            power_used += item.attributes.get(&attr_power).unwrap().value.unwrap();
+        }
+    }
+
+    ship.add_attribute(AttributeId::powerUsed, 0.0, power_used);
+}
+
+pub fn attribute_cpu_unused(ship: &mut Ship) {
+    /* How much CPU is left, which is the total CPU minus the usage. */
+
+    let attr_cpu_used = AttributeId::cpuUsed as i32;
+    let attr_cpu_output = AttributeId::cpuOutput as i32;
+
+    let cpu_used = ship
+        .hull
+        .attributes
+        .get(&attr_cpu_used)
+        .unwrap()
+        .value
+        .unwrap();
+    let cpu_output = ship
+        .hull
+        .attributes
+        .get(&attr_cpu_output)
+        .unwrap()
+        .value
+        .unwrap();
+    let cpu_unused = cpu_output - cpu_used;
+
+    ship.add_attribute(AttributeId::cpuUnused, 0.0, cpu_unused);
+}
+
+pub fn attribute_power_unused(ship: &mut Ship) {
+    /* How much PG is left, which is the total PG minus the usage. */
+
+    let attr_power_used = AttributeId::powerUsed as i32;
+    let attr_power_output = AttributeId::powerOutput as i32;
+
+    let power_used = ship
+        .hull
+        .attributes
+        .get(&attr_power_used)
+        .unwrap()
+        .value
+        .unwrap();
+    let power_output = ship
+        .hull
+        .attributes
+        .get(&attr_power_output)
+        .unwrap()
+        .value
+        .unwrap();
+    let power_unused = power_output - power_used;
+
+    ship.add_attribute(AttributeId::powerUnused, 0.0, power_unused);
+}
diff --git a/src/calculate/pass_4/scan_strength.rs b/src/calculate/pass_4/scan_strength.rs
new file mode 100644
index 0000000..9e686a1
--- /dev/null
+++ b/src/calculate/pass_4/scan_strength.rs
@@ -0,0 +1,30 @@
+use super::super::Ship;
+use super::AttributeId;
+
+static SCAN_STRENGTH_ATTRIBUTES: [i32; 4] = [
+    AttributeId::scanRadarStrength as i32,
+    AttributeId::scanLadarStrength as i32,
+    AttributeId::scanMagnetometricStrength as i32,
+    AttributeId::scanGravimetricStrength as i32,
+];
+
+pub fn attribute_scan_strength(ship: &mut Ship) {
+    /* Scan Strength can be one of 4 scan strength values (radar, ladar, magnetometric, gravimetric). */
+
+    let mut base_scan_strength = 0.0;
+    let mut scan_strength = 0.0;
+    for attribute_id in SCAN_STRENGTH_ATTRIBUTES.iter() {
+        if ship.hull.attributes.contains_key(attribute_id) {
+            let attribute = ship.hull.attributes.get(attribute_id).unwrap();
+
+            if attribute.base_value > base_scan_strength {
+                base_scan_strength = attribute.base_value;
+            }
+            if attribute.value.unwrap() > scan_strength {
+                scan_strength = attribute.value.unwrap();
+            }
+        }
+    }
+
+    ship.add_attribute(AttributeId::scanStrength, base_scan_strength, scan_strength);
+}