Chapter 17 – Understanding Memory Allocation and Lifetime

1. In addition to an identifier, a data type, and a value, variables also have a storage class, a lifetime, and visibility (or scope).
2. The four storage classes are auto, static, extern (global), and register.
3. The lifetimes of static and external storage classes begin when the program loads (each is created) and end when the program ends (each is destroyed).
4. A static variable is only visible within the block or compilation unit (file) where it is declared.
5. An external (global) variable is visible to every function and block within the compilation unit (file) where it is declared.
6. Automatic variables are destroyed/no longer accessible after execution leaves the block where they are declared.