Variables

A variable is an abstraction of a storage location that can hold a value

How many variables are in this program?

def fact(x: Int): Int = {
    if (x < 2) {
        1
    } else {
        x * fact(x - 1)
    }
}

x is a variable, but at runtime, each recursion creates an instance of x, and each of these instances needs a different storage location.

The extent of a variable instance is the time interval when the instance can be accessed

The compiler keeps a symbol table that maps each variable to its offset from the frame pointer. The symbol table exists at compile time only.