Abstract
ABACUS, a Battersea Automatic Computer Unit for Study, is a digital computer system designed and built expressly for teaching and demonstration purposes. It is intended mainly for the instruction of Computer Technology students. The prototype machine was built in the Electrical and Control Engineering Department of the University of Surrey. This thesis describes, first, the conception of the computing system as a whole, with the reasoned choice of the system capability and operating parameters. Thereafter, the thesis is only concerned with the Arithmetic Unit, which forms the nucleus of the system. Details of the mechanical construction of the Arithmetic Unit are given; the Logic is described in terms of the Registers and circulations and then in detail, function by function. The section 'Abacus in use' describes how the machine has been used as an advanced teaching aid and adopted as a commercial enterprise by Elliott Automation, As an aid to students and teachers, the second part of the section describes the detailed evolution of the Logic of the primitive design which later became the prototype. The final section contains the author's conclusions resulting from the building of the machine, with discussion of the value and originality of the project.