To the present day the history of banking software is nearly untold. While there is already some literature on the use of computers in the banking industry, most of it focuses only on the hardware and its restrictions (cf. Cortada 2006). The logic behind these machines remains untold. With the advent of the computer as a universal machine since the 1950s, business processes have been written into code, not hard wired into the machine. Furthermore, not the processor but the system software steered what was presented on the screen to the banking employee. Hardware got more and more exchangeable, while the real guiding principles of computing in action are to be found in software. This article analyzes how German savings banks used software to digitalize their business during the period of the Cold War.