Hungarian-born John von Neumann ... computer's internal memory (RAM), and they would be executed to process the data that were also fed into the same memory. Contrast with Harvard architecture.

program counter (PC) - holds the memory address of the next instruction to be fetched from primary memory memory address register (MAR) - holds the address of the current instruction that is to be ...

The registers and key elements of the Von Neumann architecture all play a part in how an instruction is processed in the fetch-decode-execute cycle.