Angus Lothian
--- a/b_asic/operation.py
+++ b/b_asic/operation.py
        If no neighbours are found this returns an empty list
        """
        raise NotImplementedError
+
+
+class AbstractOperation(Operation, AbstractGraphComponent):
+    """Generic abstract operation class which most implementations will derive from.
+    TODO: More info.
--- a/b_asic/operation.py
+++ b/b_asic/operation.py
+    _output_ports: List["OutputPort"]
+    _parameters: Dict[str, Optional[Any]]
+
+    def __init__(self, name: Name = ""):
+        super().__init__(name)
+        self._input_ports = []
+        self._output_ports = []
+        self._parameters = {}
+
+    @abstractmethod
+    def evaluate(self, *inputs) -> Any: # pylint: disable=arguments-differ
+        """Evaluate the operation and generate a list of output values given a
+        list of input values."""
+        raise NotImplementedError
+
+    def inputs(self) -> List["InputPort"]:
--- a/b_asic/operation.py
+++ b/b_asic/operation.py
+
+    def params(self) -> Dict[str, Optional[Any]]:
+        return self._parameters.copy()
+
+    def param(self, name: str) -> Optional[Any]:
+        return self._parameters.get(name)
+
+    def set_param(self, name: str, value: Any) -> None:
+        assert name in self._parameters # TODO: Error message.
+        self._parameters[name] = value
+
+    def evaluate_outputs(self, state: SimulationState) -> List[Number]:
+        # TODO: Check implementation.
+        input_count: int = self.input_count()
+        output_count: int = self.output_count()
+        assert input_count == len(self._input_ports) # TODO: Error message.
--- a/b_asic/operation.py
+++ b/b_asic/operation.py
+    def params(self) -> Dict[str, Optional[Any]]:
+        return self._parameters.copy()
+
+    def param(self, name: str) -> Optional[Any]:
+        return self._parameters.get(name)
+
+    def set_param(self, name: str, value: Any) -> None:
+        assert name in self._parameters # TODO: Error message.
+        self._parameters[name] = value
+
+    def evaluate_outputs(self, state: SimulationState) -> List[Number]:
+        # TODO: Check implementation.
+        input_count: int = self.input_count()
+        output_count: int = self.output_count()
+        assert input_count == len(self._input_ports) # TODO: Error message.
+        assert output_count == len(self._output_ports) # TODO: Error message.
--- a/test/port/test_inputport.py
+++ b/test/port/test_inputport.py
    assert s_w_source.source.signals == [s_w_source]
    assert s_w_source.destination is None

+def test_connect_then_disconnect(inp_port, out_port):
+    """Can port be connected and then disconnected properly?"""
+    inp_port.connect(out_port)
+