Complete chapter 15 exercises

Author: Stratus3D

chapter_15/README.md

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+# Exercises for Chapter 15
+
+**1. Download the code for the port driver given earlier and test it.**
+
+Nothing needed for this exercise.
+
+**2. Download code for a linked in driver and test it on your system**
+
+The book says to download drivers from git://github.com/erlang/linked_in_drivers.git but this repository no longer exists.
+
+**3. Find an operating system command to discover what kind of CPU your computer has. Write a function that returns your CPU type using the `os:cmd/1`**
+
+Solution in the `exercise_3/` directory.
+
+```
+erlc cpu_info.erl
+erl
+1> cpu_info:get().
+[{"Architecture","x86_64"},
+ {"CPU op-mode","32-bit, 64-bit"},
+ {"Model name","Intel(R) Core(TM) i7-5500U CPU @ 2.40GHz"},
+ ...
+2> cpu_info:get("Model name").
+"Intel(R) Core(TM) i7-5500U CPU @ 2.40GHz"
+```