Vonneumann model of computer architecture

VONNEUMANN MODEL The von Neumann model of computer architecture wasfirst described in 1946 in the famous paper by Burks, Goldstein, and vonNeumann (1946). A number of very early computers or computerlike devices hadbeen built, starting with the work of Charles Babbage, but the simple structureof a stored‑program computer was first described in thislandmark paper. The authors pointed out that instructions and data consist ofbits with no distinguishing characteristics. Thus a common memory can be usedto store both instructions and data. The differentiationbetween these two is made by the accessing mechanism and context; the programcounter accesses instructions while the effective address register accessesdata. If by some chance, such as a programming error, instructions and data areexchanged in memory, the performance of the program is indeterminate. Beforevon Neumann posited the single address space architecture, a number ofcomputers were built that had disjoint instruction and data memories. One ofthese machines was built by Howard Aiken at Harvard University, leading to thisdesign style being called a Harvard architecture. A variation onthe von Neumann architecture that is widely used for implementing calculatorstoday is called a tagged architecture. With these machines, each data type inmemory has an associated tag that describes the data type: instruction,floating-point value (engineering notation), integer, etc. When the calculatoris commanded to add a floating‑point number to aninteger, the tags are compared; the integer is converted tofloating point, the addition is performed, and the result is displayed infloating point. You can try this yourself with your scientific calculator. Memory Thecomputer will have memory that can hold both data and also the programprocessing that data. In modern computers this memory is RAM. Image result for von neumann architecture images ControlUnit Thecontrol unit will manage the process of moving data and program into and out ofmemory and also deal with carrying out (executing) program instructions - oneat a time. This includes the idea of a 'register' to hold intermediate values.In the illustration above, the 'accumulator' is one such register. Image result for von neumann architecture images Input- Output Thisarchitecture allows for the idea that a person needs to interact with themachine. Whatever values that are passed to and forth are stored once again insome internal registers. Image result for von neumann architecture images ArithmeticLogic Unit Thispart of the architecture is solely involved with carrying out calculations uponthe data. All the usual Add, Multiply, Divide and Subtract calculations will beavailable but also data comparisons such as 'Greater Than', 'Less Than', 'EqualTo' will be available. Bus Noticethe arrows between components? This implies that information should flowbetween various parts of the computer. In a modern computer built to the VonNeumann architecture, information passes back and forth along a 'bus'. Thereare buses to identify locations in memory - an 'address bus' Image result for von neumann architecture images