When it comes to understanding the von Neumann architecture, it is necessary to understand the previous architecture of the ENIAC computer. The computer hardware consists of various vacuum tubes that are arranged in such a way to process data. Special computers are all the instructions are known in advance and what need to be done is just fetch in data, process them, and produce results. John von Neumann invented a nice architecture for general purpose computer which is still used. These architecture rules are not used in the hardware but treated in the same way as data. Binary codes are fetched into the CPU. Codes have the same length as data ones and contain information about what operations to run and specific addresses to read or write. The two essential parts of the von Neumann architecture are the Arithmetic Logic Unit (CA) and the Program Control Unit (CC) that are combined to form the Central Processing Unit (CPU). The main function of a computer, as the name implied, is to compute or specifically perform certain arithmetic (add, subtract, multiple, divide) and logic (comparisons) operations; this is carried out by the central arithmetical (CA) part of the computer. The CA is however unable to make computations by itself, there is, instead a special part that tell CA what kind of operations to perform, what sequence of instructions to be carried out, where to look for the parameters (data), and where to store the results of operations. This part actually controls the program stored in the memory and is so called Program Control Unit (CC).

With these two essential parts, the Main Memory (M) is important in von Neumann architecture. The Main Memory is the place to keep data and instructions stored as binary codes ready to flow in the CPU. Without this component, CPU would need to take information from external storage devices such as