In Chapter 3, Tables and Objects, you learned how to use one of Lua's most powerful features: tables. This chapter will build on that knowledge by introducing the global table, some of Lua's built-in modules, and how to create custom modules. By the end of this chapter, you should be able to put classes into modules to make them as reusable as possible. 

In this chapter, we will cover the following topics:

• The global table 
• The Lua math library
• The Lua file IO library 
• Interfacing with the operating system
• More strings
• Creating and loading modules