Today it’s hard to believe, but computers, without which many can no longer imagine their life, appeared only some 70 years ago. One of those who made a decisive contribution to their creation was the American scientist John von Neumann. He proposed the principles on which to this day most computers work. Consider how the von Neumann machine works.
Brief curriculum vitae
Janos Neumann was born in 1930 in Budapest, in a very wealthy Jewish family, who subsequently managed to get a noble title. From childhood, he was distinguished by outstanding abilities in all areas. At 23, Neumann already defended his thesis in experimental physics and chemistry. In 1930, a young scientist was invited to work in the United States, at Princeton University. At the same time, Neumann became one of the first employees of the Institute for Advanced Studies, where he worked as a professor until the end of his life. Neumann's scientific interests were quite extensive. In particular, he is one of the creators of the apparatus of quantum mechanics and the concept of cellular automata.
Contribution to Computer Science
Before figuring out what principle von Neumann architecture does not comply with, it will be interesting to learn how the scientist came to the idea of ​​creating a modern type of computer.
As an expert in the mathematics of explosions and shock waves, in the early 1940s, von Neumann was a scientific consultant in one of the laboratories of the United States Army Ammunition Administration. In the fall of 1943, he arrived in Los Alamos to participate in the development of the Manhattan project at the personal invitation of its leader Robert Oppenheimer. He was tasked with calculating the force of implosive compression of the charge of an atomic bomb to a critical mass. To solve it, large calculations were required, which at first were carried out on manual calculators, and later on IBM mechanical tabulators, using punch cards.
Von Neumann got acquainted with the information on the development of electronic-mechanical and fully electronic computers. Soon he was involved in the development of EDVAC and ENIAC computers, as a result of which he began to write the first draft of the EDVAC report, which remained incomplete, in which he presented to the scientific community a completely new idea of ​​what computer architecture should be.
Von Neumann principles
By 1945, informatics as a science reached a dead end, since all computers stored in their memory the processed numbers in the 10th form, and programs for performing operations were set by setting jumpers on the patch panel.
This greatly limited the capabilities of computers. The real breakthrough was von Neumann's principles. Briefly, they can be expressed in one sentence: the transition to a binary number system and the principle of a stored program.
Analysis
Consider the principles on which the classical structure of the von Neumann machine is based, in more detail:
1. Transition to binary from decimal
This principle of Neumann architecture allows the use of fairly simple logical devices.
2. Software control of an electronic computer
Computer operation is controlled by a set of commands executed sequentially one after another. The development of the first machines with a program stored in memory laid the foundation for modern programming.
3. Data and programs in computer memory are stored together
At the same time, both the data and the program commands have the same way of writing in the binary number system, so in certain situations it is possible to perform the same actions on them as on the data.
The consequences
In addition, the architecture of the Fonneimann machine has the following features:
1. Memory cells have addresses that are numbered sequentially
Thanks to the application of this principle, the use of variables in programming has become possible. In particular, at any time you can refer to a particular memory cell at its address.
2. The possibility of conditional transition during the execution of the program
As already mentioned, commands in programs must be executed sequentially. However, it is possible to make a transition to any part of the code.
How does von Neumann machine work
Such a mathematical model consists of a memory (memory), an arithmetic logic device (ALU), a control device, as well as input and output devices. All program commands are recorded in memory cells located in the neighborhood, and data for their processing is written in arbitrary cells.
Any team should consist of:
- instructions on which operation should be performed;
- addresses of memory cells that store the source data affected by the specified operation;
- cell addresses to which the result should be written.
The operations indicated by the commands on specific source data are performed by the ALU, and the results are recorded in memory cells, i.e., stored in a form convenient for subsequent machine processing, or transferred to an output device (monitor, printer, etc.) and become available to humans.
UU controls all parts of the computer. From it, the other devices receive “what to do” orders, and from other devices it receives information about the state in which they are.
The control device has a special register called the “command counter” of the SC. After loading the initial data and the program into the memory, the SK records the address of its 1st command. UU reads from the computer memory the contents of the cell whose address is in the SC, and places it in the "Command Register". The control device determines the operation corresponding to a specific command and “notes” in the computer memory the data whose addresses are indicated in it. Next, the ALU or computer hardware proceeds to perform the operation, after which the contents of the SC changes by one, i.e. indicates the next command.
Criticism
The flaws and current perspectives of von Neumann architecture continue to be the subject of debate. The fact that machines created on the principles advanced by this outstanding scientist are not perfect was noticed a very long time ago.
Therefore, in examinations on computer science one often encounters the question "what principle does von Neumann architecture not comply with and what disadvantages does it have?"
When responding to its second part, you must indicate:
- the presence of a semantic gap between high-level programming languages ​​and the command system;
- on the problem of matching the OP and processor bandwidth;
- the emerging software crisis, caused by the fact that the cost of its creation is much lower than the cost of developing hardware, and there is no way to fully test the program;
- lack of prospects in terms of speed, since its theoretical limit has already been reached.
As for which principle the von Neumann architecture does not comply with, it is a question of the parallel organization of a large number of data streams and instructions inherent in a multiprocessor architecture.
Conclusion
Now you know what principle von Neumann architecture does not comply with. It is obvious that science and technology do not stand still, and, very soon, computers of a completely new type will appear in every home, thanks to which mankind will reach a new level of its development. By the way, the simulator program “von Neumann Architecture” will help prepare for the exam. Such digital educational resources facilitate the assimilation of material and provide an opportunity to evaluate your knowledge.