Page:VN First Draft Report EDVAC Moore Sch 1945.pdf/9



1.1 The considerations which follow deal with the structure of a, and in particular with its logical control. Before going into specific details, some general explanatory remarks regarding these concepts may be appropriate.

1.2 An is a (usually highly composite) device, which can carry out instructions to perform calculations of a considerable order of complexity — e.g. to solve a non-linear partial differential equation in 2 or 3 independent variables numerically.

The instructions which govern this operation must be given to the device in absolutely exhaustive detail. They include all numerical information which is required to solve the problem under consideration: Initial and boundary values of the dependent variables, values of fixed parameters (constants), tables of fixed functions which occur in the statement of the problem. These instructions must be given in some form which the device can sense: Punched into a system of punchcards or on teletype tape, magnetically impressed on steel tape or wire, photographically impressed on motion picture film, wired into one or more fixed or exchangeable plugboards — this list being by no means necessarily complete. All these procedures require the use of some code, to express the logical and the algebraical definition of the problem under consideration, as well as the necessary numerical material (cf. above).

Once these instructions are given to the device, it must be able to carry them out completely and without any need for further intelligent human intervention. At the end of the required operations the device must record the results again in one of the forms referred to