Notations of the Analytical Engine

These 388 notations describe how the Analytical Engine functions. They are meant to accompany the mechanical details of the engine given in the Series A drawings.

Most of the notations, except in the earliest part of the series, are 'walk throughs' or 'traces' of micro-programs for the different versions of the Analytical Engine. They explain the complex algorithms that Babbage planned to use to perform the various arithmetic functions of addition, subtraction, multiplication, division, extraction of square root and sub-tabulation. The notations allow us to infer much of the functional arrangement and most of the sequence control of the various plans of the Analytical Engine.

There are many variations of the Analytical Engine's algorithms. The basic techniques evolved rapidly throughout the first phase of Babbage's work on the engine. Many of the plans represent evolving ideas for the arithmetic algorithms and their control mechanisms that are reflected in the logical structure of the machine, rather than major mechanical innovations. However, algorithmic and mechanical innovations did proceed in parallel with, and interact with, one another.

The notations are created and arranged in sets, consisting of large sheets of paper, or multiple sheets glued together, folded to a convenient size.