diff --git a/src/emulator/__init__.py b/src/emulator/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/main.py b/src/emulator/main.py
similarity index 100%
rename from src/main.py
rename to src/emulator/main.py
diff --git a/src/optable.py b/src/emulator/optable.py
similarity index 100%
rename from src/optable.py
rename to src/emulator/optable.py
diff --git a/src/vm.py b/src/emulator/vm.py
similarity index 98%
rename from src/vm.py
rename to src/emulator/vm.py
index b2d9b8e..f46a060 100644
--- a/src/vm.py
+++ b/src/emulator/vm.py
@@ -37,6 +37,7 @@ class VMExceptionType(Enum):
 class VMException(Exception):
     cause: VMExceptionType
     pc: int
+    message: str = ""
 
 @dataclass
 class VM:
@@ -125,7 +126,8 @@ class VM:
         if self._to_raw_bytes_offset(self.pc) > len(self.mem) - WORD_SIZE:
             raise VMException(
                     VMExceptionType.END_OF_MEM,
-                    self.pc.value
+                    self.pc.value,
+                    "couldn't perform step because end of memory occured"
                     )
         opcode, *_ = instr = self._fetch_instr()
         opdesc = self._get_opcode_desc(opcode)
@@ -175,7 +177,8 @@ class VM:
         if not opcode in OPCODES:
             raise VMException(
                     VMExceptionType.INVALID_OPCODE,
-                    self.pc.value
+                    self.pc.value,
+                    f"Couldn't resolve an opcode {hex(opcode)}"
                     )
         return OPCODES[opcode]