diff --git a/src/shardware.adb b/src/shardware.adb
index 3ee9ffa..2a69a10 100644
--- a/src/shardware.adb
+++ b/src/shardware.adb
@@ -232,4 +232,40 @@ package body Shardware is
     end if;
   end DivF;
 
+  function CmpU (Register : Unsigned_32; Value : Unsigned_32) return Boolean is 
+  begin
+    if Register = Value then
+      return True;
+    else
+      return False;
+    end if;
+  end CmpU;
+
+  function CmpI (Register : Integer; Value : Integer) return Boolean is 
+  begin
+    if Register = Value then
+      return True;
+    else
+      return False;
+    end if;
+  end CmpI;
+
+  function CmpF (Register : Float; Value : Float) return Boolean is 
+  begin
+    if Register = Value then
+      return True;
+    else
+      return False;
+    end if;
+  end CmpF;
+
+  function Jump (Address : Unsigned_32) return Unsigned_32 is 
+  begin
+    if Address mod 2 = 0 then
+      return Address;
+    else
+      raise Constraint_Error with "Can only jump to start of the line";
+    end if;
+  end Jump;
+
 end Shardware;
diff --git a/src/shardware.ads b/src/shardware.ads
index 23c7fa1..99e4295 100644
--- a/src/shardware.ads
+++ b/src/shardware.ads
@@ -46,4 +46,10 @@ package Shardware is
   procedure DivI (Register : in out Integer; Value : Integer);
   procedure DivF (Register : in out Float; Value : Float);
 
+  function CmpU (Register : Unsigned_32; Value : Unsigned_32) return Boolean;
+  function CmpI (Register : Integer; Value : Integer) return Boolean;
+  function CmpF (Register : Float; Value : Float) return Boolean;
+
+  function Jump (Address : Unsigned_32) return Unsigned_32;
+
 end Shardware;
diff --git a/src/sillymachine.adb b/src/sillymachine.adb
index c29d362..326848f 100644
--- a/src/sillymachine.adb
+++ b/src/sillymachine.adb
@@ -19,13 +19,15 @@ procedure sillymachine is
   ExecSize : Integer := 0;
   MemorySize : Integer := 0;
 
-  PC : Integer := 0; -- Program Counter
+  PC : Unsigned_32 := 0; -- Program Counter
   Instruction : ByteArr (0 .. 15);
 
   RegisterU : RegArrU (0 .. 27);
   RegisterI : RegArrI (0 .. 27);
   RegisterF : RegArrF (0 .. 27);
 
+  ZeroFlag : Boolean := False;
+
 begin
 
   
@@ -106,7 +108,7 @@ begin
     PC := 64; -- initialise program counter to entry point
     while True loop
       for i in 0 .. 15 loop -- load the instruction
-        Instruction (i) := MemoryArr (PC + i);
+        Instruction (i) := MemoryArr (Integer(PC) + i);
       end loop;
 
       case MyShiftU(Instruction (0), 8) + Unsigned_32(Instruction (1)) is -- execute the instruction
@@ -175,6 +177,30 @@ begin
           BytesToF(TempBytes(Instruction)));
         when 34 => DivF(RegisterF(Integer(Instruction(2))),             -- Divide Register by Register (Float)
           RegisterF(Integer(Instruction (3))));
+        when 35 => ZeroFlag := CmpU(RegisterU(Integer(Instruction(2))),
+          BytesToU(TempBytes(Instruction)));
+        when 36 => ZeroFlag := CmpU(RegisterU(Integer(Instruction(2))),
+          RegisterU(Integer(Instruction (3))));
+        when 37 => ZeroFlag := CmpI(RegisterI(Integer(Instruction(2))),
+          BytesToI(TempBytes(Instruction)));
+        when 38 => ZeroFlag := CmpI(RegisterI(Integer(Instruction(2))),
+          RegisterI(Integer(Instruction (3))));
+        when 39 => ZeroFlag := CmpF(RegisterF(Integer(Instruction(2))),
+          BytesToF(TempBytes(Instruction)));
+        when 40 => ZeroFlag := CmpF(RegisterF(Integer(Instruction(2))),
+          RegisterF(Integer(Instruction (3))));
+        when 41 =>
+          if ZeroFlag then
+            PC := Jump(BytesToU(TempBytes(Instruction)));
+          else
+            null;
+          end if;
+        when 42 =>
+          if ZeroFlag then
+            null;
+          else
+            PC := Jump(BytesToU(TempBytes(Instruction)));
+          end if;
         when 65535 => goto THE_END; -- exit opcode
         when others => null;
       end case;