Winter 2021 report to the Computer Conservation Society

Project Report to Computer Conservation Society Committee for Meeting Thursday 18 November 2021

The project has reached a long-awaited defining point. Tim Robinson has completed the first draft of the most comprehensive description yet of the Analytical Engine designs. We have for the first time both an aerial view that integrates partial and seemingly unrelated developments, as well as the most detailed analysis yet of the specifics of implementation.

This analysis has been a prerequisite for the build. Babbage left no design for a complete Engine and the rationale for the ad hoc improvements made over thirty-eight years has not, till now, been fully investigated nor understood. We have lacked the necessary understanding to inform a meaningful build i.e. which signature features of which design should be combined to create a single representative machine.

The treatise, which is a product of five years research founded on a comprehensive review of the entire technical archive, describes six phases of development from 1832 through till Babbage’s death in 1871. At user level, Tim describes and analyses the use of punched cards, the designs for the ‘Great Operations’ (multiplication, division, square root), and for the ‘Small Operations’ (including addition, subtraction, and stepping). The description and running analysis run to some 120,000 words and includes close studies of selected mechanisms. 

Our immediate next step is to structure and edit the material into a form usable by others. This is both to ensure the preservation of the knowledge the document represents, and to provide a working datum for the next stage. We are seeking to appoint someone on a funded basis to collaborate with Tim to produce a document to publishable standards.

In parallel with this we are set to examine the working papers of the late Prof. Allan Bromley. Anne Bromley, Allan’s widow, has donated three large binders of material to the Science Museum and we have made arrangements to access this material at the Science Museum Library in the Dana Centre in South Kensington. The Science Museum has kindly permitted us to copy the material for research purposes. 

Bromley’s publications on the Analytical Engine are masterful, invaluable but regrettably sparse and the extent of his very considerable understanding of the designs is certainly underrepresented in his published output. The examination of these papers will, it is hoped, corroborate our new understanding as well as reveal just how far he had succeeded in decoding Babbage’s intentions.

Doron Swade

 

 

Autumn 2021 report to the Computer Conservation Society

Submitted by Doron Swade to the Computer Conservation Society.

Winding back to last Spring, with the survey of the Babbage manuscript archive complete, we were faced with the choice of pressing on to define what might be built using our current knowledge, or stepping back to evaluate and analyse what was captured in the review of the archive. We decided to step back and Tim Robinson has made substantial progress extending and integrating our understanding of the AE design and its trajectory from 1834 till Babbage’s death in 1871. Tim has identified and describes six phases in the evolution of the AE designs.

These are framed in an overview of the developmental timeline of the whole AE enterprise. There are also focussed pieces on central topics including the use of punched cards, the user view, methods of carriage of tens, and arithmetical process. This work represents the first comparative overview of each of the major designs ('Plans') and provides a new depth of understanding of the overall AE designs and of the developmental arc. The new findings vindicate the decision to take time out to process the material from the archive survey: the work will inform what can meaningful be built given that none of Babbage’s original designs describe a complete engine; secondly, the scholarly value of capturing and documenting a major advance in understanding since Bruce Collier’s work in the 1960s and Allan Bromley’s work in the 1970s and 80s. The immediate next step is to complete this analysis. The project will then move on to defining what version of the AE should be built.

Doron Swade

Spring 2021 report to the Computer Conservation Society

Submitted by Doron Swade to the Computer Conservation Society.

Tim Robinson has started writing up findings following the review of the complete Babbage manuscript archive. The initial work is in the form of an overview centred on each of the ‘Plans’ i.e. the large ‘systems drawings’ that Babbage shed during the evolution of the designs. The intention was to put to one side further detailed work, for the moment at least, to take stock and to document broad-stroke findings and new insights. Excavating further the hardly-known Plan 30 (there is a Plan 28a but seemingly no Plan 29) proved irresistible both for inherent interest and for completeness. Babbage restarted work on the AE designs in June 1857 after a break of almost a decade and referred to the machine as ‘Analytical Engine 30’. Tim reports that the hardware changes introduced for Plan 30 are ‘dramatic’. One remarkable feature is the extension of the Store to 1000 registers, and most intriguingly various methods of mechanically addressing the store contents. The broad-stroke writing has been paused temporarily while this rich seam is explored. It is not expected to take long and we look forward do the resumption of the interpretative account.

Doron Swade 

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