From 47e0041c8696b3e731c5452f76bd956529773927 Mon Sep 17 00:00:00 2001
From: kdeng00 <kundeng94@gmail.com>
Date: Wed, 4 Nov 2020 21:20:39 -0500
Subject: [PATCH] Demo on the uses of the static reserved word

---
 ch_04/static_demo/compile.sh |  5 ++++
 ch_04/static_demo/main.c     | 25 ++++++++++++++++++++
 ch_04/static_demo/number.c   | 44 ++++++++++++++++++++++++++++++++++++
 ch_04/static_demo/number.h   | 12 ++++++++++
 4 files changed, 86 insertions(+)
 create mode 100755 ch_04/static_demo/compile.sh
 create mode 100644 ch_04/static_demo/main.c
 create mode 100644 ch_04/static_demo/number.c
 create mode 100644 ch_04/static_demo/number.h

diff --git a/ch_04/static_demo/compile.sh b/ch_04/static_demo/compile.sh
new file mode 100755
index 0000000..e76077d
--- /dev/null
+++ b/ch_04/static_demo/compile.sh
@@ -0,0 +1,5 @@
+#!/bin/bash
+
+
+
+gcc main.c number.c -I. -std=gnu99 -o a.out
diff --git a/ch_04/static_demo/main.c b/ch_04/static_demo/main.c
new file mode 100644
index 0000000..5392956
--- /dev/null
+++ b/ch_04/static_demo/main.c
@@ -0,0 +1,25 @@
+/*
+ *
+ * Demonstration of static variables (External and internal) and functions.
+ *
+ * Author: Kun Deng
+ */
+
+#include <stdio.h>
+
+#include <number.h>
+
+
+int main()
+{
+    const int number_limit = 10;
+    printf("Printing %d numbers\n", number_limit);
+
+    for (int i = 0; i != number_limit; ++i)
+    {
+        printf("%d: %d\n", i, Number_get_number());
+    }
+
+
+    return 0;
+}
diff --git a/ch_04/static_demo/number.c b/ch_04/static_demo/number.c
new file mode 100644
index 0000000..a87ce70
--- /dev/null
+++ b/ch_04/static_demo/number.c
@@ -0,0 +1,44 @@
+#include <stdlib.h>
+
+#include "number.h"
+
+/* Variable will only be accessible from this file because
+ * it's static
+ */
+static int number = 1;
+
+
+static void do_something()
+{
+    /* Retains the value outside of the scope
+     * because it's an internal static variable.
+     */
+    static int changer = 1;
+
+    number += changer;
+
+    if (changer % 10 >= 4)
+    {
+        changer += 5;
+    }
+    else if (changer % 10 < 4)
+    {
+        changer += 3;
+    }
+    else
+    {
+        changer *= 2;
+    }
+}
+
+
+
+int Number_get_number()
+{
+    extern int number;
+
+    do_something();
+
+    return number;
+}
+
diff --git a/ch_04/static_demo/number.h b/ch_04/static_demo/number.h
new file mode 100644
index 0000000..b82bbbf
--- /dev/null
+++ b/ch_04/static_demo/number.h
@@ -0,0 +1,12 @@
+
+
+/* Does something to a number. This function is static and
+ * will not be accessible outside of this file. Functions and
+ * variables defined as static are not visible to outside
+ * files. This function is private to this file and can only
+ * be called from within.
+ */
+static void do_something(void);
+
+
+int Number_get_number(void);