diff --git a/education/software development/ECE1400/Chapter 14 Exercises.md b/education/software development/ECE1400/Chapter 14 Exercises.md
index ad27a20..2d24f30 100644
--- a/education/software development/ECE1400/Chapter 14 Exercises.md	
+++ b/education/software development/ECE1400/Chapter 14 Exercises.md	
@@ -1 +1,13 @@
+> **12.** Suppose that the macro `M` has been defined as follows:
+```c
+#define M 10
+```
+> Which of the following tests will fail?
+```c
+// C will fail, because `M` is defined.
+#ifndef M
+```
+
+---
+
 > **13.** Show what the following program will look like after preprocessing. You may ignore any lines added to the program as a result of including the `<stdio.h>` header.