132: Mainline

The rules for global variables—those defined outside of any function—are quite different:

• Global variable values are available to all functions that are defined after the global variable is defined, except in functions in which there is a parameter or local variable that happens to have the same name. Such parameters or local variables are said to shadow the corresponding global variables.
• In places where a global variable value is not shadowed, its value can be changed by an assignment statement. The change affects all subsequent evaluation of the global variable.