January 2021 report to the Computer Conservation Society

Presented by Doron Swade on Monday 21 January 2021 to the Computer Conservation Society.

With the first-pass inspection of the manuscript archive complete, attention has turned to analysis and interpretation, and organising the findings to aid navigation. Babbage shed versions of the design as it developed in the form of ‘Plans’ – large ‘systems drawings’ which serve as developmental staging posts – the main ones of which number Plan 1 through to Plan 28. The overall approach to analysing the accumulated data is that of a timeline that groups all material, from wherever in the archive (drawings, Notebooks, Notations), to each of the landmark Plans.

The significance of the design advances for each Plan is identified as each is reviewed and evaluated, whether, for example, a new Plan involves a major design reset or only incremental change. From this, the first fruits of the extensive study of the sources are now emerging and the overall developmental arc is now easier to identify. A major initial finding is that the designs are less disjointed than thought and there is more continuity in the inventive trajectory than we feared was the case, or that scholarship to date had indicated. As an example of a more specific finding: it is not until Plan 27 that there is the first evidence of user-level conditional operation. While the Analytical Engine is routinely portrayed as incorporating, from the start, defining features of a modern computer conditional operation included, this feature appears fairly late in the day and is barely mentioned again. How significant to Babbage was conditional operation as a defining feature, is now an enticing open question.

This work is being undertaken by Tim Robinson in the US. Progress was slowed in by climate crises in California not to mention political and pandemic disruption. The initial findings are a long-awaited reward after some four years examining primary sources.

Doron Swade