From a4ee663899b4301052c47156ad17ce42f98e315b Mon Sep 17 00:00:00 2001
From: talksik <ap@talksik.com>
Date: Thu, 24 Sep 2026 15:06:50 -0700
Subject: [PATCH] understand static and extern

---
 ch4/helper.h |  3 +++
 ch4/main.c   | 19 +++++++++++++++++++
 ch4/other.c  |  8 ++++++++
 3 files changed, 30 insertions(+)
 create mode 100644 ch4/helper.h
 create mode 100644 ch4/main.c
 create mode 100644 ch4/other.c

diff --git a/ch4/helper.h b/ch4/helper.h
new file mode 100644
index 0000000..ca17d75
--- /dev/null
+++ b/ch4/helper.h
@@ -0,0 +1,3 @@
+
+
+extern int sum;
diff --git a/ch4/main.c b/ch4/main.c
new file mode 100644
index 0000000..3452ddc
--- /dev/null
+++ b/ch4/main.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include "helper.h"
+
+void increment();
+
+int main() {
+  printf("hello world\n");
+
+  increment();
+  increment();
+
+  printf("sum within main: %d\n", sum);
+
+  sum++;
+
+  printf("sum within main: %d\n", sum);
+
+  return 0;
+}
diff --git a/ch4/other.c b/ch4/other.c
new file mode 100644
index 0000000..a94971f
--- /dev/null
+++ b/ch4/other.c
@@ -0,0 +1,8 @@
+#include <stdio.h>
+#include "helper.h"
+
+int sum = 0;
+
+void increment() {
+  sum++;
+}