EDVAC and Its Codes
Von Neumann’s meshing routine is written for a virtual EDVAC with a different architecture from the machine described in the famous First Draft of a Report on the EDVAC. This chapter describes the ‘programmers’ interface’ and the code of both versions of the machine. The familar EDVAC of the First Draft is described in relation to the proposals for the Bell Labs Relay Calculator, and the unfamiliar manuscript reproduced in Appendix A allows us to give a detailed description of how the plans for EDVAC had evolved by the summer of 1945. The revised code that von Neumann proposed and used in the meshing routine is described in detail. Examples of the use of the both codes are given and the way that von Neumann laid out the code in the manuscript is explained. The notion of substitution is identified as the unifying concept underlying von Neumann’s design of these codes.