On the occasion of the upcoming 40th anniversary of the publication of Aufschreibesysteme 1800/1900 by Friedrich Kittler, the article returns to this work and examines its core term, “Aufschreibesystem”, which is also the basic concept underpinning his media theory. It examines the reasons why “Aufschreibesystem” is translated as “discourse network” in British and American academic circles, and verifies its true meaning from an etymological perspective: inscription system. Additionally, the article explores the origin and relationship between the concept and Shannon-Weaver's information theory, Foucault’s “extériorit”, Lacan’s psychoanalysis and Derrida’s grammatology, and reveals the specific connotations of “inscription”, “transformation”, “surface”. In addition, it outlines the world picture of its “inscription” by comparing the relevant thoughts of Foucault, Lacan and Derrida. This views not only opens up many aspects of Kittler’s media theory that have long been neglected and obscured, but also reveals the methodological basis of his media theory,and leaves a unique and valuable ideological legacy for analysing both history and the present.