Babbage´s Analytical Engine Plans 28 and 28a. The programmer´s interface

Between 1843 and 1846 Charles Babbage worked intensively on the design of Plan 28 of his Analytical Engine. Most of his effort was devoted to the development of the great operations of multiplication, division, and addition/subtraction of strings of operands. These were carefully elaborated, and the implementations of both multiplication and division have a decidedly modern flavor. Some of Babbage´s time was spent on small operations including implementations of conditional branches. Here we find revealed for the first time a workable, if unpolished, user instruction set for the programmer of his Analytical Engine.