Tuesday, May 3, 2016

Further progress as reported to the Computer Conservation Society

Progress continues decoding Babbage’s Mechanical Notation – the language of signs and symbols Babbage devised to describe the mechanisms of his calculating Engines. There has been a new archival find in manuscript papers Babbage gave to a younger colleague, Harry Wilmot Buxton. The Buxton papers are held by the Museum of the History of Science, Oxford. The papers were known about and some material has been published but last time the papers were viewed predates the focussed interest on the Analytical Engine, and the significance of the material on the Mechanical Notation passed unnoticed. With the kind permission of the archivist, permission was given for a copying rostrum to be used and the relevant material was digitally photographed in situ. The significance of the material is two- fold: it contains Babbage’s efforts to provide generalised rules for annotating his mechanical drawings; secondly, the principles it documents confirms our findings from the earlier exercise in which knowledge of the Difference Engine mechanisms were used to decode the Notations that describe them – this without the benefit of generalised rules of syntax orgrammar. The agreement between the archive and our earlier findings is a satisfying vindication of the decoding method using known mechanisms.

The Ada Lovelace bicentennial, celebrated this year, has directed attention to the Analytical Engine through the description of the Engine Lovelace published in 1843. Her description of the Engine is in the form of Notes which form a substantial addendum to the account by Luigi Menabrea who wrote up some of Babbage’s lectures on the Analytical Engine Babbage gave in Turin in 1840. The ongoing preparation of celebratory exhibitions, symposia andmedia coverage, has redirected attention to specific features of Lovelace’s description. One such is the use control arrangements between the punched card input and the routing of information between the cards, processor and memory. It appears that there is no form of indexed or relative addressing either of which would be required for the AE to execute the example given by Lovelace - the calculation of Bernoulli numbers. It is far from clear how the Engine executes its control functions and there are several ongoing collaborative conversations between scholars and historians analysing the issue stimulated by the extended interest in Lovelace’s work. The lesson we have taken is that much as is known about the principles of the AE, there is much that is not understood at the fundamental level of internal control and such understanding is a prerequisite of any construction, physical or virtual.

Doron Swade

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