In the 1960s, Brinch Hansen worked at the Danish computer company Regnecentralen, first in the compiler group headed by Peter Naur and Jørn Jensen, and, later, as the chief architect of the RC 4000 minicomputer and its renowned operating system kernel (RC 4000 Multiprogramming System).
From 1959 to 1969, he was employed at Regnecentralen, the Danish computing institute, while at the same time giving lectures at the Niels Bohr Institute and the Technical University of Denmark.