In the column "Who ? ", the Frankfurter Allgemeine Zeitung published a report in the section "Technik und Motor":

"March 1, in San Francisco, the Computer Pioneer Award of the Institute of Electrical and Electronics Engineers (IEEE) was presented to Professor Friedrich L. Bauer, Ordinarius for Mathematics and Informatics at the Technische Universität München. He received this 'Nobel Prize for Engineers', which had been granted before, among others, to Konrad Zuse, Niklaus Wirth and Heinz Zemanek, for his invention of the Keller-Prinzip."

The stack principle was the result of investigations Bauer and his late friend Klaus Samelson carried out with the example of arithmetic formulae with invisible bracketing: A computer which is required to read (from left to right) 3+5*8+4*7, is disallowed from starting with the addition 3+5; instead "3+" is to be postponed and 5*8 is to be computed first, according to the rule "Times binds stronger than Plus" or shorter "Dot dominates Dash". However, after 5*8 is evaluated to be 40, the postponed addition "3+" can be finished, resulting in the intermediate result 43, which in turn is postponed until 4*7 has been treated. This is the optimal procedure according to the motto: "So wenig als nötig zurückstellen und sobald als möglich nachholen". It means that the operation postponed last is carried out first, which is the stack principle. A stack (German Keller) is a last in, first out store.

The Computer Pioneer medal, embellished by an engraving of Babbage

The stack principle is of far-reaching importance. It found a natural extension to all bracketed operation structures and all bracketed data structures; Bauer comprises this under the name "Cellar Principle of State Transition and Storage Allocation ". Today, the stack principle is permanently applied and has influenced computer architecture as well as programming languages.

Wilfried.Brauer@informatik.tu-muenchen.de