In the context of Culture, Human code or Human-readable code is to machine code as Human language is to Machine language.
This context extends into computer science as a relationship between and amongst coders and the users of computing machines. Whilst root users and normal users share the machines, they do not necessarily share language familiarity. For this reason the use of metaphors is often important in cultures of both machines and Humans.
Computing has consistently involved development courses and practices that insure a manual override capability from the earliest concepts onward. In cantrast to the recency of the arts and sciences of computing, Humanity, and the Human condition has held a code that predates computing by an amount that is pretty much indeterminable except perhaps if one were to use something like the geologic time scale for example as a frame of reference.
As the field of Computer science expands, the computing equipment and software comes closer to "understanding" the human code or so it is argued by the proponents of Artificial Intelligence and Artificial life. The question as to the complexity of the culture that embodies development courses and practices then would logically have to be answered, at least to move the science further along the paths chosen to date.