diff --git a/src/Expression.cpp b/src/Expression.cpp
new file mode 100644
index 0000000..43fcaf7
--- /dev/null
+++ b/src/Expression.cpp
@@ -0,0 +1,79 @@
+/*
+// Copyright (c) 2017 Intel Corporation
+// Copyright (c) 2022 IBM Corp.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+*/
+
+#include "Expression.hpp"
+
+#include <stdexcept>
+
+namespace expression
+{
+std::optional<Operation> parseOperation(std::string& op)
+{
+    if (op == "+")
+    {
+        return Operation::addition;
+    }
+    if (op == "-")
+    {
+        return Operation::subtraction;
+    }
+    if (op == "*")
+    {
+        return Operation::multiplication;
+    }
+    if (op == R"(%)")
+    {
+        return Operation::modulo;
+    }
+    if (op == R"(/)")
+    {
+        return Operation::division;
+    }
+
+    return std::nullopt;
+}
+
+int evaluate(int a, Operation op, int b)
+{
+    switch (op)
+    {
+        case Operation::addition:
+        {
+            return a + b;
+        }
+        case Operation::subtraction:
+        {
+            return a - b;
+        }
+        case Operation::multiplication:
+        {
+            return a * b;
+        }
+        case Operation::division:
+        {
+            return a / b;
+        }
+        case Operation::modulo:
+        {
+            return a % b;
+        }
+
+        default:
+            throw std::invalid_argument("Unrecognised operation");
+    }
+}
+} // namespace expression