Demo on the uses of the static reserved word

ch_04/static_demo/compile.sh

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+#!/bin/bash
+
+
+
+gcc main.c number.c -I. -std=gnu99 -o a.out

ch_04/static_demo/main.c

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+/*
+ *
+ * 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;
+}

ch_04/static_demo/number.c

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+#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;
+}
+

ch_04/static_demo/number.h

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+
+
+/* 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);