Merge pull request #4731 from Rageking8/add-example-for-c2018

Add example for C2018

Author: Jak-MS

docs/error-messages/compiler-errors-1/compiler-error-c2018.md

@@ -11,3 +11,21 @@ ms.assetid: 86b54573-dca0-4446-be1a-e3ac489c073b
 unknown character 'hexnumber'
 
 The source file contains an unexpected ASCII character, which is identified by its hex number. To resolve the error, remove the character.
+
+The following sample generates C2018:
+
+```cpp
+// C2018.cpp
+int main() {
+   @   // C2018
+}
+```
+
+Possible resolution:
+
+```cpp
+// C2018b.cpp
+int main() {
+
+}
+```