Electronic Computing Circuits of ENIAC

Summary-The ENIAC (Electronic Numerical Integrator and Computer), the first electronic computing machine to be built, is a very large device (containing 18,000 vacuum tubes) compounded out of a few basic types of computing circuits. The design principles that were followed in order to insure reliable operation of the electronic computer are presented, and the basic types of computing circuits are analyzed. Most of the design work on component circuits was devoted to constructing reliable memory circuits (ffip-flops) and adding circuits (counters). These are treated in detail. The ENIAC performs the operations of addition, subtraction, multiplication, division, square-rooting, and the looking up of function

values automatically. The units which perform these operations, the units which take numerical data into and out of the machine, and those which control the over-all operation are described. The technique of combining the basic electronic circuits to perform these functions is illustrated by three typical computing circuits: the addition circuit, a programming circuit, and the multiplication circuits

I.              INTRODUCTION

HE ENIAC (Electronic Numerical Integrator and Computer) is the first general-purpose computing machine in which the computation is done entirely electronically. It is the purpose of this paper to discuss the design of the various circuits used and to show how they are combined to make an automatically sequenced electronic computer. As an introduction, however, it is worth while to consider the general question: What is the function of the ENIAC? That is, what kinds of problems does it solve?

Very briefly, the answer to this question is that the ENIAC can solve any problem which can be reduced to numerical computation, i.e., to a finite sequence (of reasonable length) consisting of additions, subtractions, multiplications, divisions, square-rootings, and the looking up of function values. Hence, it can differentiate, integrate, solve systems of imultaneous algebraic and transcendental equations, partial differential equations, etc. The importance of high-speed electronic computation derives from the fact that there are many problems that the mathematical physicist can easily formulate but which can be solved only with great labor. The differential equations of exterior ballistics will serve as a good example of this, especially since the ENIAC was designed primarily to solve total differential equations of about this order of complexity.


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