Charles Babbage's Analytical Engine, 1838

Abstract

Charles Babbage commenced work on the design of the Analytical Engine in 1834 following the collapse of the project to build the Difference Engine. His ideas evolved rapidly, and by 1838 most of the important concepts used in his later designs were established. This paper introduces the design of the Analytical Engine as it stood in early 1838, concentrating on the overall functional organization of the mill (or central processing portion) and the methods generally used for the basic arithmetic operations of multiplication, division, and signed addition. The paper describes the working of the mechanisms that Babbage devised for storing, transferring, and adding numbers and how they were organized together by the "microprogrammed" control system; the paper also introduces the facilities provided for user- level programming. The intention of the paper is to show that an automatic computing machine could be built using mechanical devices, and that Babbage's designs provide both an effective set of basic mechanisms and a workable organization of a complete machine.