In June 1945 John von Neumann circulated the "First Draft of a Report on the EDVAC," a document describing a computer architecture where program and data share the same memory. This principle — the stored program — is the fundamental difference between a fixed calculator and a reprogrammable computer: instead of rewiring the machine to change its function, it is enough to load a new program into memory. Von Neumann architecture defines the structural pattern followed by practically all modern processors: arithmetic-logic unit, control unit, memory, and input/output system. Turing had theoretically formalized the concept; von Neumann translated it into engineering specification.