diff --git a/.gitignore b/.gitignore
index d902cf9..f0aebc1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 *.ods#
 docs/*.pdf
+__pycache__
diff --git a/emulator/emulator.py b/emulator/emulator.py
index d32a47a..0bb841f 100644
--- a/emulator/emulator.py
+++ b/emulator/emulator.py
@@ -3,7 +3,11 @@
 
 from typing import BinaryIO
 
+ROM_SIZE = 0x700
 MAX_INT = 0x1000
+MAX_IMMEDIATE = 0x80
+
+class ConfigurationError(Exception): pass
 
 
 class Device:
@@ -37,10 +41,14 @@ class Memory:
         rom: list[int],
         devices: list[Device] | None = None,
     ) -> None:
-        self._rom = [0] * 0x700
+        self._rom = [0] * ROM_SIZE
         self._devices = (devices or list())[:]
         self._ram = [0] * 0x1000
 
+        if len(rom) > ROM_SIZE:
+            raise ConfigurationError(
+                f"ROM too long: {hex(len(rom))} > {hex(ROM_SIZE)}")
+
         for i, data in enumerate(rom):
             self._rom[i] = data % MAX_INT
 
@@ -84,13 +92,29 @@ class Memory:
             with open(file, 'b') as f:
                 while f:
                     incoming = f.read(3)
-                    rom.append(incoming[0] << 4 | ((incoming[1] & 0xf0) >> 4))
-                    rom.append(((incoming[1] & 0xf) << 8) | incoming[2])
+                    if len(incoming) == 3:
+                        rom.append(incoming[0] << 4 | ((incoming[1] & 0xf0) >> 4))
+                        rom.append(((incoming[1] & 0xf) << 8) | incoming[2])
+                    elif len(incoming) == 2:
+                        rom.append(incoming[0] << 4 | ((incoming[1] & 0xf0) >> 4))
+                        rom.append(((incoming[1] & 0xf) << 8))
+                    elif len(incoming) == 1:
+                        rom.append(incoming[0] << 4)
+                    else:
+                        break
         else:
             while file:
                 incoming = file.read(3)
-                rom.append(incoming[0] << 4 | ((incoming[1] & 0xf0) >> 4))
-                rom.append(((incoming[1] & 0xf) << 8) | incoming[2])
+                if len(incoming) == 3:
+                    rom.append(incoming[0] << 4 | ((incoming[1] & 0xf0) >> 4))
+                    rom.append(((incoming[1] & 0xf) << 8) | incoming[2])
+                elif len(incoming) == 2:
+                    rom.append(incoming[0] << 4 | ((incoming[1] & 0xf0) >> 4))
+                    rom.append(((incoming[1] & 0xf) << 8))
+                elif len(incoming) == 1:
+                    rom.append(incoming[0] << 4)
+                else:
+                    break
 
         return rom
 
@@ -223,8 +247,14 @@ class Computer:
     def interrupt(self, index: int):
         self._interrupt_flag.append(index % MAX_INT)
 
-    def step(self):
+    def step(self, verbose: bool = False):
         instruction = self._mem[self.program_counter]
+        if verbose:
+            print(
+                f"; {hex(self.program_counter)} : {oct(instruction)} "
+                f"({hex(instruction)})"
+            )
+            self.verbose_step()
 
         if instruction == 0: self.NOP()
         elif instruction == 1: self.HLT()
@@ -240,28 +270,125 @@ class Computer:
         elif instruction & 0xFF8 == 0x38: self.POP(instruction & 0x7)
         elif instruction & 0xF80 == 0x80: self.LDI(instruction & 0x7F)
         elif instruction & 0xFC0 == 0x100:
-            self.LSH(instruction & 0x38, instruction & 0x7)
+            self.LSH((instruction & 0x38) >> 3, instruction & 0x7)
         elif instruction & 0xFC0 == 0x140:
-            self.RSH(instruction & 0x38, instruction & 0x7)
+            self.RSH((instruction & 0x38) >> 3, instruction & 0x7)
         elif instruction & 0xFC0 == 0x180:
-            self.INC(instruction & 0x38, instruction & 0x7)
+            self.INC((instruction & 0x38) >> 3, instruction & 0x7)
         elif instruction & 0xFC0 == 0x1C0:
-            self.DEC(instruction & 0x38, instruction & 0x7)
-        elif instruction & 0xE0 == 0x200:
-            self.AND(instruction & 0x1C, instruction & 0x38, instruction & 0x7)
-        elif instruction & 0xE0 == 0x400:
-            self.OR(instruction & 0x1C, instruction & 0x38, instruction & 0x7)
-        elif instruction & 0xE0 == 0x600:
-            self.NAD(instruction & 0x1C, instruction & 0x38, instruction & 0x7)
-        elif instruction & 0xE0 == 0x800:
-            self.SUB(instruction & 0x1C, instruction & 0x38, instruction & 0x7)
-        elif instruction & 0xE0 == 0xA00:
-            self.XOR(instruction & 0x1C, instruction & 0x38, instruction & 0x7)
-        elif instruction & 0xE0 == 0xC00:
-            self.NOR(instruction & 0x1C, instruction & 0x38, instruction & 0x7)
-        elif instruction & 0xE0 == 0xE00:
-            self.ADD(instruction & 0x1C, instruction & 0x38, instruction & 0x7)
-        else: raise LookupError()
+            self.DEC((instruction & 0x38) >> 3, instruction & 0x7)
+        elif instruction & 0xE00 == 0x200:
+            self.AND(
+                instruction & 0x7,
+                (instruction & 0x38) >> 3,
+                (instruction & 0x1C0) >> 6,
+            )
+        elif instruction & 0xE00 == 0x400:
+            self.OR(
+                instruction & 0x7,
+                (instruction & 0x38) >> 3,
+                (instruction & 0x1C0) >> 6,
+            )
+        elif instruction & 0xE00 == 0x600:
+            self.NAD(
+                instruction & 0x7,
+                (instruction & 0x38) >> 3,
+                (instruction & 0x1C0) >> 6,
+            )
+        elif instruction & 0xE00 == 0x800:
+            self.SUB(
+                instruction & 0x7,
+                (instruction & 0x38) >> 3,
+                (instruction & 0x1C0) >> 6,
+            )
+        elif instruction & 0xE00 == 0xA00:
+            self.XOR(
+                instruction & 0x7,
+                (instruction & 0x38) >> 3,
+                (instruction & 0x1C0) >> 6,
+            )
+        elif instruction & 0xE00 == 0xC00:
+            self.NOR(
+                instruction & 0x7,
+                (instruction & 0x38) >> 3,
+                (instruction & 0x1C0) >> 6,
+            )
+        elif instruction & 0xE00 == 0xE00:
+            self.ADD(
+                instruction & 0x7,
+                (instruction & 0x38) >> 3,
+                (instruction & 0x1C0) >> 6,
+            )
+        else:
+            raise LookupError(
+                f"Cannot find instruction "
+                f"{hex(self.program_counter)}: {oct(instruction)}"
+            )
+
+    def verbose_step(self):
+        instruction = self._mem[self.program_counter]
+
+        if instruction == 0: print("NOP")
+        elif instruction == 1: print("HLT")
+        elif instruction == 2: print("INT")
+        elif instruction == 3: print("BNZ")
+        elif instruction == 4: print("BLK")
+        elif instruction == 5: print("ENB")
+        elif instruction & 0xFF8 == 0x10: print(f"GLA {instruction & 0x7}")
+        elif instruction & 0xFF8 == 0x18: print(f"GET {instruction & 0x7}")
+        elif instruction & 0xFF8 == 0x20: print(f"LOD {instruction & 0x7}")
+        elif instruction & 0xFF8 == 0x28: print(f"STR {instruction & 0x7}")
+        elif instruction & 0xFF8 == 0x30: print(f"PSH {instruction & 0x7}")
+        elif instruction & 0xFF8 == 0x38: print(f"POP {instruction & 0x7}")
+        elif instruction & 0xF80 == 0x80: print(f"LDI {instruction & 0x7F}")
+        elif instruction & 0xFC0 == 0x100:
+            print(f"LSH {instruction & 0x7} {(instruction & 0x38) >> 3}")
+        elif instruction & 0xFC0 == 0x140:
+            print(f"RSH {instruction & 0x7} {(instruction & 0x38) >> 3}")
+        elif instruction & 0xFC0 == 0x180:
+            print(f"INC {instruction & 0x7} {(instruction & 0x38) >> 3}")
+        elif instruction & 0xFC0 == 0x1C0:
+            print(f"DEC {instruction & 0x7} {(instruction & 0x38) >> 3}")
+        elif instruction & 0xE00 == 0x200:
+            print(
+                f"AND {instruction & 0x7} {(instruction & 0x1C0) >> 6} "
+                f"{(instruction & 0x38) >> 3}"
+            )
+        elif instruction & 0xE00 == 0x400:
+            print(
+                f"OR {instruction & 0x7} {(instruction & 0x1C0) >> 6} "
+                f"{(instruction & 0x38) >> 3}"
+            )
+        elif instruction & 0xE00 == 0x600:
+            print(
+                f"NAD {instruction & 0x7} {(instruction & 0x1C0) >> 6} "
+                f"{(instruction & 0x38) >> 3}"
+            )
+        elif instruction & 0xE00 == 0x800:
+            print(
+                f"SUB {instruction & 0x7} {(instruction & 0x1C0) >> 6} "
+                f"{(instruction & 0x38) >> 3}"
+            )
+        elif instruction & 0xE00 == 0xA00:
+            print(
+                f"XOR {instruction & 0x7} {(instruction & 0x1C0) >> 6} "
+                f"{(instruction & 0x38) >> 3}"
+            )
+        elif instruction & 0xE00 == 0xC00:
+            print(
+                f"NOR {instruction & 0x7} {(instruction & 0x1C0) >> 6} "
+                f"{(instruction & 0x38) >> 3}"
+            )
+        elif instruction & 0xE00 == 0xE00:
+            print(
+                f"ADD {instruction & 0x7} {(instruction & 0x1C0) >> 6} "
+                f"{(instruction & 0x38) >> 3}"
+            )
+        else:
+            print(
+                f"LookupError: Cannot find instruction "
+                f"{hex(self.program_counter)}: {oct(instruction)}"
+            )
 
     # === Operations ===
 
@@ -315,7 +442,7 @@ class Computer:
         self.program_counter += 1
 
     def LDI(self, Immediate: int):
-        self.pointer = Immediate % 0x3F
+        self.pointer = Immediate % MAX_IMMEDIATE
         self.program_counter += 1
 
     def LSH(self, REG_D: int, REG_A: int):
diff --git a/emulator/main.py b/emulator/main.py
index 49b7b2d..6dce04b 100644
--- a/emulator/main.py
+++ b/emulator/main.py
@@ -6,15 +6,12 @@ from typing import Sequence
 from .emulator import Computer, Memory
 from .devices import tty
 
-
-def simple_computer_with_tty(rom: list[int]) -> Computer:
-    return Computer(Memory(rom, [tty(0x7FE, 0x7FF)]))
-
-def main(argv: Sequence[str]):
+def main(argv: Sequence[str] | None = None):
     import argparse
+    from time import sleep
 
     machines = {
-        'tty': simple_computer_with_tty
+        'tty': lambda rom: Computer(Memory(rom, [tty(0x7FE, 0x7FF)]))
     }
 
     parser = argparse.ArgumentParser(
@@ -23,14 +20,36 @@ def main(argv: Sequence[str]):
     parser.add_argument('rom_file', type=argparse.FileType('rb'))
     parser.add_argument(
         '-m', '--machine', choices=machines.keys(), default='tty')
+    parser.add_argument('-v', '--verbose', action='store_true')
+    parser.add_argument('-s', '--step', action='store_true')
+    parser.add_argument('-c', '--clock', default='100')
 
     args = parser.parse_args(argv)
 
     computer = machines[args.machine](Memory.load_rom_file(args.rom_file))
 
-    while computer.active:
-        computer.step()
+    try:
+        while computer.active:
+            if args.verbose:
+                print(
+                    f"ZR: {hex(0)} \t"
+                    f"PC: {hex(computer.program_counter)} \t"
+                    f"SP: {hex(computer.stack_pointer)} \t"
+                    f"MP: {hex(computer.pointer)}"
+                )
+                print(
+                    f"D0: {hex(computer.data_0)} \t"
+                    f"D1: {hex(computer.data_1)} \t"
+                    f"D2: {hex(computer.data_2)} \t"
+                    f"D3: {hex(computer.data_3)}"
+                )
+            if args.step:
+                input("Press enter to step to next instruction...")
+            computer.step(args.verbose)
+            if not args.step:
+                sleep(int(args.clock)/1000)
+    except KeyboardInterrupt:
+        print("Keyboard Interrupt: Program Exiting...")
 
 if __name__ == '__main__':
-    from sys import argv
-    main(argv)
+    main()
diff --git a/language/assembler.py b/language/assembler.py
index ccd35e5..32ef0b5 100644
--- a/language/assembler.py
+++ b/language/assembler.py
@@ -5,6 +5,7 @@ from collections import namedtuple
 from typing import TypeVar, Generic, Iterable, Sequence
 
 INSTRUCTIONS_COUNT = 0x700
+MAX_IMMEDIATE = 0x80
 
 class AssemblerError(Exception): pass
 class LinkerError(Exception): pass
@@ -105,10 +106,16 @@ class Instruction(namedtuple('Instruction', ['bb', 'bl', 'lb', 'll'])):
 
     def __bytes__(self) -> bytes:
         value = int(self)
-        u = value & 0xf00 >> 8
-        m = value & 0xf0 >> 4
+        u = (value & 0xf00) >> 8
+        l = value & 0xff
+        return bytes((u, l))
+
+    def hex_tuple(self) -> tuple[int, int, int]:
+        value = int(self)
+        u = (value & 0xf00) >> 8
+        m = (value & 0xf0) >> 4
         l = value & 0xf
-        return bytes((u, m, l))
+        return (u, m, l)
 
     def oct_str(self) -> str:
         return (
@@ -215,10 +222,25 @@ class Program:
 
     def __bytes__(self) -> bytes:
         output = bytearray()
+        for i in range(0, INSTRUCTIONS_COUNT, 2):
+            instruction = self._get_instruction(i)
+            u1, m1, l1 = instruction.hex_tuple()
+            output += bytes(((u1 << 4) | m1, ))
+            if i + 1 < INSTRUCTIONS_COUNT:
+                instruction = self._get_instruction(i + 1)
+                u2, m2, l2 = instruction.hex_tuple()
+                output += bytes(((l1 << 4) | u2, ))
+                output += bytes(((m2 << 4) | l2, ))
+            else:
+                output += bytes((l1 << 4, ))
+        return bytes(output)
+
+    def hex_str(self) -> str:
+        output = ""
         for i in range(INSTRUCTIONS_COUNT):
             instruction = self._get_instruction(i)
-            output += bytes(instruction)
-        return bytes(output)
+            output += f"{hex(int(instruction))}\n"
+        return output
 
     def labels(self) -> dict[str, int]:
         return self._label_map.copy()
@@ -229,7 +251,7 @@ class Program:
         else: _, value = self._instructions[new_index]
         if isinstance(value, Immediate):
             return self.instruction_set["LDI"](
-                f"LDI {self._label_map[value.value]}", -1)
+                f"LDI {self._label_map[value.value] -1}", -1)
         elif isinstance(value, Directive):
             raise LinkerError("Unexpected directive!")
         else:
@@ -300,7 +322,8 @@ class Program:
                 last_error = e
                 print(f"Error:\n\t{e}")
         if last_error is not None:
-            raise last_error
+            # raise last_error
+            exit()
 
         return instructions
 
@@ -370,17 +393,21 @@ def immediate(line: str, line_number: int) -> Instruction | Immediate:
         else:
             value = int(args[1], base=0)
 
-        return Instruction(
-            0,
-            2 + ((value & 0x040) >> 6),
-            (value & 0x038) >> 3,
-            value & 0x007,
-        )
+            if value >= MAX_IMMEDIATE:
+                raise AssemblerError(
+                    f"Immediate value too large {line_number}: {args[1]}")
+
+            return Instruction(
+                0,
+                2 + ((value & 0x040) >> 6),
+                (value & 0x038) >> 3,
+                value & 0x007,
+            )
     else:
         raise AssemblerError(
             f"Invalid number of arguments on line {line_number}: {args[0]}")
 
-def main(argv: Sequence[str]):
+def main(argv: Sequence[str] | None = None):
     import argparse
     parser = argparse.ArgumentParser(
         description='ytd 12-bit Computer Linker and Assembler',
@@ -388,11 +415,23 @@ def main(argv: Sequence[str]):
     parser.add_argument('input_file', type=argparse.FileType('r'))
     parser.add_argument('-o', '--output_file', type=argparse.FileType('wb'))
     parser.add_argument('-l', '--labels_file', type=argparse.FileType('w'))
+    parser.add_argument('-x', '--hex_file', type=argparse.FileType('w'))
 
     args = parser.parse_args(argv)
 
     program = Program(args.input_file.read())
 
+    try: assert len(bytes(program)) <= INSTRUCTIONS_COUNT * 1.5
+    except AssertionError:
+        print(
+            hex(int(len(bytes(program)) / 1.5)),
+            '>',
+            hex(INSTRUCTIONS_COUNT),
+            ':',
+            hex(int(len(bytes(program)) / 1.5) - INSTRUCTIONS_COUNT),
+        )
+        raise
+
     if args.output_file:
         args.output_file.write(bytes(program))
 
@@ -400,6 +439,8 @@ def main(argv: Sequence[str]):
         for label, location in program.labels().items():
             args.labels_file.write(f"{hex(location)}, {label}\n")
 
+    if args.hex_file:
+        args.hex_file.write(program.hex_str())
+
 if __name__ == '__main__':
-    from sys import argv
-    main(argv)
+    main()
diff --git a/language/examples/test1.s b/language/examples/test1.s
index fe1c746..f95f689 100644
--- a/language/examples/test1.s
+++ b/language/examples/test1.s
@@ -2,9 +2,19 @@
 ; Example 1 - ytd 12-bit Computer
 ; Fibonacci
 
-.0x5
+; .0x5
 main:
-    ; Initialize values
+    ; Load Output Device Address
+    ldi 0x7F
+    or D3 MP ZR
+    lsh D3 D3
+    lsh D3 D3
+    lsh D3 D3
+    lsh D3 D3
+    ldi 0xE
+    or D3 MP D3
+
+    ; Initialize Fibonacci values
     ldi 1
     or D0 MP ZR
     or D1 ZR ZR
@@ -12,7 +22,7 @@ main:
 
 loop:
     ; Output current value
-    ldi 0x7FE
+    or MP D3 ZR
     str D0
 
     ; Move values down