Add example for fatal error C1012

Author: Rageking8

docs/error-messages/compiler-errors-1/fatal-error-c1012.md

@@ -1,13 +1,21 @@
 ---
-description: "Learn more about: Fatal Error C1012"
 title: "Fatal Error C1012"
-ms.date: "11/04/2016"
+description: "Learn more about: Fatal Error C1012"
+ms.date: "02/20/2025"
 f1_keywords: ["C1012"]
 helpviewer_keywords: ["C1012"]
-ms.assetid: 92cc83a7-b5b8-4da8-a128-9b7ccb510496
 ---
 # Fatal Error C1012
 
-unmatched parenthesis : missing character
+unmatched parenthesis: missing 'character'
 
 The parentheses in a preprocessor directive do not match.
+
+The following sample generates C1012:
+
+```cpp
+// C1012.cpp
+// compile with: /c
+#if (0   // C1012
+#endif
+```