diff --git a/gbso/program.py b/gbso/program.py
index 070ed60..48ddb10 100644
--- a/gbso/program.py
+++ b/gbso/program.py
@@ -1,19 +1,19 @@
 from dataclasses import dataclass
-from typing import List, Set
+from typing import Dict, List, Optional, Set, Union
 
-from gbso.cpu import CPU
+from gbso.cpu import CPU, CPUState
 from gbso.insn import Insn
 from gbso.regs import R8
 
 
 @dataclass
 class Program:
-    outputs: Set[R8]
+    outputs: Set[Union[R8, int]]
     insns: List[Insn]
+    init_state: Optional[CPUState] = None
 
-    # TODO: Memory outputs
-    # TODO: Initialization of registers/memory
-
-    def execute(self, cpu: CPU) -> None:
+    def execute(self) -> CPU:
+        cpu = CPU(state=self.init_state)
         for insn in self.insns:
             insn.exec(cpu)
+        return cpu