diff --git a/src/simulator/register.rs b/src/simulator/register.rs
index 4cbe50d..2f78d30 100644
--- a/src/simulator/register.rs
+++ b/src/simulator/register.rs
@@ -1,3 +1,5 @@
+use crate::simulator::machine::{NUM_FP_REGS, NUM_INT_REGS};
+
 use std::ops::{Add,  Sub};
 
 pub trait RegisterNum: Add<Output=Self> + Sub<Output=Self> + PartialEq + Copy {}
@@ -20,7 +22,10 @@ impl<U: RegisterNum> Register<U> {
 		self.register[position as usize]
 	}
 
-	/// Set value of register *position* to *value* 
+	/// Set value of register *position* to *value*
+    /// 
+    /// Checking against trying to set a new value to the 0th register
+    /// as its value is NOT supposed to change
 	pub fn set_reg(&mut self, position: usize, value: U) {
 		if position != 0 { self.register[position] = value; }
 	}
@@ -33,7 +38,7 @@ impl Register<i64> {
 	/// i64 register constructor
 	pub fn init() -> Register<i64> {
 		Register { 
-			register: [0i64; 32]
+			register: [0i64; NUM_INT_REGS]
 		}
 	}
 
@@ -44,7 +49,7 @@ impl Register<f32> {
 	/// f32 register constructor
 	pub fn init() -> Register<f32> {
 		Register { 
-			register: [0f32; 32]
+			register: [0f32; NUM_FP_REGS]
 		}
 	}