diff --git a/src/cpu.mpy b/src/cpu.mpy
index 85d8cf4..c8dc73d 100644
--- a/src/cpu.mpy
+++ b/src/cpu.mpy
@@ -1,3 +1,5 @@
+import sys
+
 class CPU:
   def __init__(self):
     self.running = False
@@ -9,41 +11,82 @@ class CPU:
 
   def load_memory(self, bytes):
     self.memory = bytes + bytearray(256 - len(bytes))
-    print(self.memory)
+    print('mem 254', self.memory[254])
+    # print(self.memory)
+
+  def start(self):
+    self.running = True
 
   def step(self):
     if self.IP >= 256:
       self.IP = 0
-    print(self.IP)
+    print("IP:", self.IP)
     self.instruction['opcode'] = self.memory[self.IP]
     self.IP = self.IP+1
     self.instruction['operand'] = self.memory[self.IP]
     self.IP = self.IP+1
-    print(self.instruction)
- 
-  nums2mnems = {
-    'hlt': '00',
-    'nop': '01',
-    'add_lit': '04'
-  }
-    
-  def hlt(self):
-    self.running = false
+    print("instr:", self.instruction['opcode'], self.instruction['operand'])
+    print("mnem:", self.nums2mnems[self.instruction['opcode']])
+    self.nums2mnems[self.instruction['opcode']](self, self.instruction['operand'])
+    print("acc:", self.acc)
+    print("running:", self.running)
+    print()
+    if not self.running:
+      sys.exit()
 
-  def nop(self):
+  def hlt(self, operand):
+    self.running = False
+
+  def nop(self, operand):
     pass
 
-  def add_lit(num):
-    self.acc = self.acc + num
+  def add_lit(self, operand):
+    self.acc = self.acc + operand
+
+  def add_mem(self, operand):
+    self.acc = self.acc + self.memory[operand]
+
+  def jmp_lit(self, operand):
+    self.IP = operand
+
+  nums2mnems = {
+    0: hlt,
+    1: nop,
+    2: 'lda_lit',
+    3: 'sta_lit',
+    4: add_lit,
+    5: 'sub_lit',
+    6: jmp_lit,
+    7: 'ske',
+    8: 'skz',
+    9: 'skn',
+    10: 'skc',
+    11: 'cst',
+    12: 'ccl',
+    16: 'hlt',
+    17: 'nop',
+    18: 'lda_mem',
+    19: 'sta_mem',
+    20: add_mem,
+    21: 'sub_mem',
+    22: 'jmp_mem',
+    23: 'ske',
+    24: 'skz',
+    25: 'skn',
+    26: 'skc',
+    27: 'cst',
+    28: 'ccl',
+  }
 
 cpu = CPU()
-print(cpu)
-print(cpu.running)
 
 prog = '04 01 14 01 00 00'
-b = bytes.fromhex(prog)
-cpu.load_memory(b)
+program_bytes = bytes.fromhex(prog)
+# Add jmp at addr 254:
+program_with_jump = program_bytes + bytearray(254 - len(program_bytes)) + bytes.fromhex('06 00')
+cpu.load_memory(program_with_jump)
 
+cpu.start()
 cpu.step()
 cpu.step()
 cpu.step()