The von Neumann architecture is the basic design described in John von Neumann’s 1945 “First Draft of a Report on the EDVAC.” The report breaks a computer into a central arithmetic part that performs operations, a central control part that sequences them, a memory, and input and output organs, the elements that together form a general-purpose computing machine.
Its defining feature is a single memory that stores both the program’s instructions and the data those instructions operate on. The control unit fetches instructions from memory one at a time, decodes them, and directs the arithmetic unit to act, while results flow back into the same memory.
This organization made the stored-program idea concrete and easy to build, and it became the template for the digital computers that followed. The terms central processing unit, main memory, and input/output still map directly onto the parts the EDVAC report named.
The architecture is sometimes contrasted with the Harvard design, which uses separate memories for instructions and data. The single shared memory of the von Neumann layout is what gives it its flexibility, and also what creates the von Neumann bottleneck between the processor and memory.