Originally a member of the Brazilian avant-garde scene which developed Concrete art in Brazil in the 1950s, Waldemar Cordeiro abandoned paint and canvas in the late 1960s to become one of the international pioneers of computer art. His achievements, interrupted as they were by his sudden and premature death in 1973, still rank among the most important early contributions to computer art. The author analyses Cordeiro’s work and highlights his late philosophical views, revealing that through his computer pieces and writings he raised many social and aesthetic issues that are still of great significance today. This article is complemented by a translation of Cordeiro’s Arteonica manifesto, written in 1971.