|of these articles describes bases of all computers. For the type of at present commercial computer see microcomputers.|
a computer, also computer, or within the private sector PC (personal computers) mentioned, is an apparatus, which can process information with the help of a programmable calculation specification. The English term computer, derived from the verb ton compute (count), designated originally humans, who made tormenting lengthy computations, for example for astronomers in the Middle Ages. Into the 60'sYears this work was settled primarily by women by calculating machines. Later the term ignored on the machines themselves.
Once the data processing with computers was limited to the processing of numbers. With increasing efficiency new areas of application opened,Computers are to be found today within all ranges of the daily life: They serve the processing and expenditure of information in economics and authorities, the computation of the statics of buildings up to the control of washing machines and automobiles. The most efficient computersare used, in order to simulate complex procedures: Examples are the climatic research, thermodynamic questions, medical computations - up to military tasks, for example the simulation of the use of nuclear weapons. Many devices of the everyday life, of the telephone over the video recorderup to the Münzprüfung in automatic vending machines, today by integrated minicomputers are steered (Embedded of system). German Konrad Zuse is considered as an inventor of the computer.
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fundamental are to be differentiated two building methods: A computer is a digital computer, if it processes digital data with digital units; it is an analog computer, if it processes similar data with similar units.
Up tofew exceptions are used today almost exclusively digital computers. These follow common basic principles, with which their free programming is made possible. With a digital computer thereby two fundamental components are differentiated: The hardware, those from the electronic, physically touchable parts of the computeris formed, as well as the software, which describes the programming of the computer.
A digital computer consists first only of hardware. The hardware makes first of all a memory in such a way specified , in that to data available as stored in drawers and at any time to the processing orExpenditure to be called up know. Secondly the arithmetic unit of the hardware has fundamental components for a free programming, with which any processing logic for data can be represented: These components are in principle the computation, the comparison, and that caused jump. A digital computer can add for example two numbers, which compare result with a third number and then dependent on the result either to the one or the other place of the program continue. In computer science this model becomes theoreticalby the Turing machine shown; the Turing machine represents the fundamental considerations to the predictability .
Only by software the digital computer becomes however useful. Each software is in principle a defined, functional arrangement of the components computation, comparison and conditioned jump, described above, howthe components to be arbitrarily often used can. This arrangement of the components, which is called program, is put down in the form of data in the memory of the computer. From there it can be selected and processed by the hardware. This operational principle thatDigital computer has itself since its origins in the center 20. Century not substantially changes, although the details of the technology were substantially improved.
Analogue computers function however according to another principle. With them replace similar elements (amplifier, condensers)logic programming. Analogue computers were used in former times more frequently for the simulation of control procedures (see:Control engineering), were displaced today however nearly completely by digital computers.
- the arithmetic and logic unit (arithmetic logical unit (ALU)),
- the control unit,
- the bus unit
- the memory and
- the input and output unit (EN).
The memory is a number of durchnummerierten „cells “, each of these cells can a small piece of information take up. This information becomes as binary number, thus a succession by yes/no information, in the memory cell put down - better to present than a consequence of zeros and ones. A characteristic „of Neumann architecture “is that this binary number (for example 65) can be either a part of the data (thus toExample the letter „A “), or an instruction for the CCU („jump… “).
In of Neumann architecture it is substantial that program and data a storage area divide (the data in all rule occupy the lower and the programs the upper storage area).
Opposite stand in the so-called.Harvard architecture data and programs own (physically separated) storage areas for the order, thus data write operations cannot overwrite programs.
In of Neumann architecture the control unit is responsible to know what is in which place in the memory.One can introduce oneself in such a way that the control unit has one „pointers “on a certain memory cell, in which the next instruction stands, which she has to implement. She selects this from the memory, recognizes for example „65 “, recognizes this as„Jump “. Then it goes to the next memory cell, because it must know, where it is to jump. She picks out also this value, and interprets the number as number (address so mentioned) of a memory cell. Then it sets the pointer on eventhis memory cell, in order to pick again their next instruction out there; the jump is carried out. If the instruction jumps for example instead of „“would read „reads value “, then it would change not the pointer of program, but from the address indicated in the consequence simplycontents pick out, in order to then pass it on for example to the ALU.
The task has the ALU to combine values from memory cells. She gets the values of the control unit supplied, charges her (adds for example two numbers, which the control unit from twoMemory cells selected) and returns the value to the control unit, which can use or again into a third memory cell write back the value then for a comparison.
In/output units is responsible finally to enter the initials of programs into the memory cellsto indicate and the user the results of the computation.
of Neumann architecture is to a certain extent the lowest level of the operational principle of a computer above the electricalphysical procedures in the conductive strips. The first computers were programmed also actually in such a way that onethe numbers of instructions and of certain memory cells in such a way, as it required the program, successively into the individual memory cells wrote.
In order to reduce this expenditure, programming languages developed… These generate the numbers within the memory cells, those the computer in the long run asProgram processes, from higher structures automatically.
Later determined itself repeating procedures summarized in libraries so mentioned, in order to have not to invent each mark again the wheel, z. B. interpreting a pressed keyboard key as letter „A “and therebyas number „65 “(in the ASCII - code). The libraries were bundled in superordinate libraries, which subfunctions link to complex operations (example: the announcement of a letter „A “, consisting of 20 individual black and 50 individual white points on the screen, after thatUser the key pressed „A “).
In a modern computer works a great many of these program levels over and/or. among themselves. More complex tasks are divided into subtasks, which were already worked on by other programmers, who develop again on the preliminary work of further programmers, of themLibraries it use. On the lowest level then however always is the machine code in such a way specified - that succession of numbers, on which the computer can also actually count.
major item: Computer history
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- an overview of the articles to the topic „computers “find you in the portal computer science.
- Konrad Zuse: The computer - my life's work, Springer: Berlin, 1993, ISBN 3-540-56292-3
- Ron White: Thus computer functions. A visual excursion by the computer & all this that belongs to it, Markt+Technik: Munich, 2004, ISBN 3-8272-6714-5