Left off on exercise 1.23

ch_01/exercise_01-15/main.c

@@ -0,0 +1,32 @@
+/*
+ *
+ * Exercise 1-15. Rewrite the temperature conversion program of Section 1.2 to
+ * use a function for conversion.
+ *
+ * Author: Kun Deng
+ */
+
+#include <stdio.h>
+
+#define UPPER 200
+#define LOWER 0
+#define STEP 10
+
+double convert_to_celsius(double);
+
+int main(int argc, char **argv)
+{
+    printf("%13s %13s\n", "fahrenheit", "celsius");
+
+    for (double fahrenheit = LOWER; fahrenheit <= UPPER; fahrenheit = fahrenheit + STEP)
+    {
+        printf("%13.2f %13.2f\n", fahrenheit, convert_to_celsius(fahrenheit));
+    }
+
+    return 0;
+}
+
+double convert_to_celsius(double fahrenheit)
+{
+    return ((fahrenheit - 32) * 5.0 / 9.0);
+}