The principle of using a pushdown stack is so well established in computer science that it needs no explanation in this review. What is not so well known is how that principle came to be such a fundamental part of compilers and other symbol processing software.

Bauer, a very early German computer pioneer, relates the step-by-step history of this concept from the time he first encountered it in a 1948 logic class, through its use in the development of ALGOL and the many languages that have arisen from that source. Along the way, he describes mechanical devices for checking logic expressions, a relay-based machine that led to patents on the process, and the interplay (and infighting) that resulted in the development of ALGOL. He details the contributions of such early pioneers as Heinz Rutishauser, Klaus Samelson, and John Backus, to name only a few.

This short item makes a significant contribution to the history of software and its creators. Not only does he provide little known information about the development of the ALGOL family, but he also relates unknown details about why certain national groups were missing from its development.