How do we, humans, communicate with computers, or computational machines? What are the activities do humans and machines share, what are the meeting points between the two? Eventually, how can we build concepts of these meeting points that leaves space for the proper mode of existence of both humans and machines, without subduing one to the other? Computers are machines that operates on a scale different from humans: the calculus done by machines is too fast and untangible for humans. This is why computers' activities has to be textualized, put into a form that can be understand for humans. For instance into a graphical interface, or a command line. More generally, this article tackles the problem of interface between humans and machines, the way the relation between humans and machines has been conceptualized. It is inspired both by philosophy of the modes of existence – since computers are machines with their own mode of existence – and semiotics, since computers' activities have to be converted in some sort of signs that can be read by humans. First, inspired by Gilbert Simondon, we try to understand the mode of existence of computational machines. By commenting on Turing 1936's seminal article, On Computable Numbers, we show that computational machines are at their core writing machines. But a writing based on calculus, different from the human way of writing. Writing can therefore be understood as a meeting point for humans and machines, provided we give a definition of writing that is large enough to include both humans and machines. Secondly, we examine theories that deals with the relationship between the two, mostly english-speaking theorists of interface (Manovich, Galloway) compared to french semiotics of "les écrits d'écran" ("written writing screens"). We show that both approaches share an anthropocentric conception of machines and/or writing, making the machine a mere instrument fulfilling human needs. Eventually, we propose some elements towards a non-anthropocentric semiotics, by focusing on the notions of interpretation and the spatiality of writing. This non-anthropocentric semiotics is the first step towards a semiotics that would make room for the mode of existence of computational machines, enabling us to renew the way we think our relationship to them.