1 files changed, 5 insertions, 0 deletions
diff --git a/display.h b/display.h
index b3b5a3d..e7cecc2 100644
--- a/display.h
+++ b/display.h
@@ -1 +1,6 @@
+#ifndef SUDOKU_DISPLAY_H
+#define SUDOKU_DISPLAY_H
+
 void display(struct cell board[9][9]);
+
+#endif /* SUDOKU_DISPLAY_H */