The author is applying them to a higher level where they dont belong, which i find a little silly. There is a processor, which loads and executes program instructions, and there is computer memory which holds both the instructions and the data. The earliest computing machines had fixed programs. Central processing unit cpu the central processing unit cpu is the electronic circuit responsible for executing the instructions of a. The design was published in a document called first draft of a report on the edvac. However, the first computer of this type to be actually constructed and operated was the manchester mark i, designed and built at manchester university in england siewiorek, et al. The reasons for apple, microsoft, and other vendors for restricting execution of native code are various, but mostly related to security and maintaining control of. Celuici designe une machine autoreplicative, cestadire quelle pourrait faire des copies dellememe. But harvard architecture which 8051 employs has separate data memory and separate code or program memory. For example, a desk calculator in principle is a fixed program computer. According to this model, a computer consists of two fundamental parts. Pdf in this short presentation, i clarify the difference between vonneumann architecture and harvard architecture. This design is still used in most computers produced today. Thus, the instructions are executed sequentially which is a slow process.