The formal definition of any machine

The general formula of any machine of function f is:

     p ← f(p, x)
    

• f: function of the machine
• p: present state
• x: unpredictable input

p consists of variables which are part of the machine.
The starting value of p is a defining choice.
x and p have fixed sizes and form the domain of f.
f(p, x) becomes the next state of p.

Instance of machine