A computer, also computer 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. Until into the 60's 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 opened new areas of application, computers are today within all ranges of the daily life to be found: 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 computers are 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 recorder up to the in automatic vending machines, are steered today by integrated minicomputers (Embedded of system). German Konrad Zuse is considered as an inventor of the computer.

Bases

Fundamental two building methods are to be differentiated: 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.

Except for few exceptions today almost exclusively digital computers are used. 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, which are formed from the electronic, for physically touchable parts of the computer, as well as the software, which describe the programming of the computer.

A digital computer consists first only of hardware. The hardware makes first of all a memory available in such a way specified, in which data can be stored as in drawers and be called up at any time to the processing or expenditure. 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 the conditioned 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 is illustrated theoretically by the Turing machine; 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, whereby the components can arbitrarily often be used. 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 of the digital computers 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 similar elements (amplifier, condensers) replace 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.

Hardware architecture

Today the generally used principle, which is called after its description by John von Neumann of 1946 "„of Neumann architecture "“, defines five"” main components for a computer "“:

• the arithmetic and logic unit (arithmetic-logical unit (ALU)),
• the control unit,
• the bus unit
• the memory and
• the input and output unit (EN).

In the today's computers the ALU and the control unit merged usually into a component, the CCU in such a way specified (cent ral processing unit, central processor).

The memory is a number of durchnummerierten "„cells "“, each of these cells can a small piece of information take up. This information is thus put down as binary number, a succession of yes/no information, in the memory cell - 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 for example the letter "„A "“), or an instruction for the CCU ("„jumps"… "“).

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 that data and programs are available own (physically separated) storage areas in so-called Harvard architecture, 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 "„jumps "“. 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 evenly this 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 simply contents would select, 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 two memory cells picked out) 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 and to the user the results of the computation indicate the initials of programs into the memory cells.

Software architecture

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 one in such a way wrote the numbers of instructions and of certain memory cells, as it required the program successively into the individual memory cells.

In order to reduce this expenditure, programming languages developed"… These generate the numbers within the memory cells, which the computer processes in the long run as program, from higher structures automatically.

Later determined itself repeating procedures in libraries so mentioned summarized, in order to have not to invent each mark the wheel again, e.g. interpreting a pressed keyboard key than letter "„A "“and thus than 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 the user pressed the key "„A "“).

In a modern computer a great many of these program levels over and/or among themselves works. 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, whose libraries use them. 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.

History

Major item: Computer history

See also

• "„"“you find an overview of the articles to the topic to computers in the portal computer science.

Literature

• 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

Related links

• Entire history of the computer - from abacuses to microprocessor (CCU)
• Listing of almost all computer types per built
• List of the 500 highest performance computers

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