diff --git a/c-basic/global_variable.c b/c-basic/global_variable.c
new file mode 100644
index 0000000..8add6ea
--- /dev/null
+++ b/c-basic/global_variable.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+int a;
+
+void foo(){
+    a = 10;
+}
+
+int main(){
+    a = 20;
+    printf("%d\n", a); // 20
+    foo();
+    printf("%d\n", a); // 10
+
+    return 0;
+}
\ No newline at end of file