Komputer: Béda antarrépisi

'''Komputer''' nyaetanyaéta hiji [[wiktionary:device|alat]] atawa [[wiktionary:machine|mesin]] keur nyieun [[wiktionary:calculation|itungan]] atawa kontrol operasi nu bisa ditembongkeun dina watesan [[wiktionary:numerical|numeris]] atawa [[wiktionary:logical|logis]]. Komputers dumasar kana sipat fisikna sarta nu pakait nembongkeun sababaraha hal atawa hal tina masalah dina hiji bagian, maka pakait mekanik bakal sacara otomatis ngahasilkeun "penyelesaian" tina masalah. Dasar teoritéori keur itungan makemaké komputer disebut '''[[élmu komputer]].'''

Computers may ''directly'' model the problem being solved, in the sense that the problem being solved is mapped as closely as possible onto the physical phenomena being exploited. For example, electron flows might be used to model the flow of water in a dam. Such ''analog'' computers were once common in the 1960s but are now rare. In most computers today, the problem is translated into mathematical terms, then reduced to simple [[Boolean algebra]]. Electronic circuits are then used to represent Boolean operations. Since almost all of mathematics can be reduced to Boolean operations, a sufficiently fast electronic computer is capable of attacking the majority of mathematical problems, and much, much more. This basic idea, which made modern ''digital'' computers possible, was formally identified and explored by [[Claude E. Shannon]].

Harti kecap komputer geus robah tapi tetep ngait kana kamampuhan mesin nu dipaké dina mangsana. Kecap ieu asalna dipaké pikeun ngadadarkeun jalma nu migawé itungan aritmétik and this usage is still valid (although it is becoming quite rare in the [[United States]]). The [[Oxford English Dictionary|OED2]] lists the year [[1897]] as the first year the word was used to refer to a [[mechanical calculating device]]. By [[1946]] several qualifiers were introduced by the OED2 to differentiate between the different types of machine. These qualifiers included [[analogue]], [[digital]] and [[electronic]]. However, from the context of the citation, it is obvious these terms were in use prior to 1946.

This description of implementation technologies is not exhaustive; it only covers the mainstream of development. Historically many exotic technologies have been explored and abandoned. For example, [[model (economics)|economic models]] have been constructed using water flowing through multiple-constricted channels, and between [[1903]] and [[1909]] [[Percy E. Ludgate]] developed a design for a programmable analytical machine based [[weaving]] technologies in which variables were carried in [[shuttle]]s.

By definition a general-purpose computer can solve any problem that can be expressed as a [[Computer program|program]] and executed within the practical limits set by: the [[computer storage|storage]] capacity of the computer, the size of program, the speed of program execution, and the reliability of the machine. In [[1934]] [[Alan Turing]] proved that, given the right program, any general-purpose computer could emulate the behavior of any other computer. This [[mathematical proof]] was purely [[wiktionary:theoretical|theoretical]] as no general-purpose computers existed at the time. The implications of this proof are profound, for example, any existing general-purpose computer is theoretically able to emulate, albeit slowly, any general-purpose computer that may be built in the future.

Computers with general-purpose capabilities are called [[Turing completeness|Turing-complete]] and this status is often used as the [[wiktionary:threshold|threshold]] capability that defines modern computers, however, this definition is [[wiktionary:problematic|problematic]]. Several computing devices with simplistic designs have been shown to be Turing-complete. The [[Z3]], developed by [[Konrad Zuse]] in [[1941]] is the earliest working computer that has been shown to be Turing-complete, so far (the proof was developed in [[1998]]). While the [[Z3]] and possibly other early devices may be theoretically Turing-complete they are impractical as general-purpose computers. They lie in what is humorously known as the [http://catb.org/~esr/jargon/html/T/Turing-tar-pit.html Turing Tar-Pit] - "a place where anything is possible but nothing of interest is practical" (See [http://catb.org/~esr/jargon/ The Jargon File]). Modern computers are more than theoretically general-purpose; they are also ''practical'' general-purpose tools. The modern, digital, electronic, general-purpose computer was developed, by many contributors, over an extended period from the mid [[1930s]] to the late [[1940s]], during this period many experimental machines were built that were possibly Turing-complete ([[Atanasoff Berry Computer|ABC]], [[ENIAC]], [[Harvard Mark I|Harvard Mk I]], [[Colossus]] etc see the [[History of computing hardware]]). All these machines have been claimed, at one time or another, as the first computer, but they all had limited utility as general-purpose problem-solving devices and their designs have been discarded.

During the late [[1940s]] the first design for a Stored-Program Computer was developed and documented (see [[The first draft]]) at the [[Moore School of Electrical Engineering]] at The [[University of Pennsylvania]]. The approach described by this document has become known as the [[Von Neumann architecture]], after it's only named author [[Jon von Neumann]] although others at the Moore School essentially invented the design. The [[Von Neumann architecture]] solved problems inherent in the design of the [[ENIAC]], which was then under construction, by storing the machines program in it's own memory. Von Neumann made the design available to other researchers shortly after the ENIAC was annouced in 1946. Plans were developed to implemented the design at the Moore School in a machine called the [[EDVAC]]. The [[EDVAC]] was not operational until [[1953]] due to technical difficulties in implementing a reliable memory. Other research institutes, who had obtained copies of the design, solved the considerable technical problems of implimenting a working memory before the Moore School team and implemented their own stored-program computers. In order of first successful operation the first 5 stored-program computers, that implemented the main features of the von Neumann Architecture were:

The Stored Program design defined by the von-Neumann Architecture finally allowed computers to readily exploit their general-purpose potential. By storing the computer's program in its own memory it became possible to rapidly "jump" from one instruction to another based on the result of evaluating a condition defined within the program. This condition usually evaluated data values calculated by the program and allowed programs to become highly dynamic. The design also supported the ability to automatically re-write the program as it executed - a powerful feature that must be used carefully. These features are fundamental to the way modern computers work.

The first electronic digital computers, with their large size and cost, mainly performed scientific calculations, often to support military objectives. The [[ENIAC]] was originally designed to calculate ballistics firing tables for [[artillery]], but it was also used to calculate neutron cross-sectional densities to see if the [[hydrogen bomb]] would work properly. This calculation, performed in [[December]], [[1945]] through [[January]], [[1946]] and involving over a million [[punch card]]s of [[data]], showed the design then under consideration would fail. (Interestingly, many of the most powerful [[supercomputer]]s available today are also used for [[nuclear weapon]]s [[simulation]]s.) The [[CSIRAC|CSIR Mk I]], the first [[Australia]]n stored-program computer, evaluated rainfall patterns for the [[catchment area]] of the [[Snowy Mountains]] Scheme, a large [[hydroelectric]] generation project. Others were used in [[cryptanalysis]], for example the world's first programmable (though not general-purpose) digital electronic computer, [[Colossus]], built during [[World War II]]. Despite this early focus of scientific applications, computers were quickly used in other areas.

While the technologies used in computers have changed dramatically since the first electronic, general-purpose, computers of the [[1940s]] (see [[History of computing hardware]] for more details), most still use the [[von Neumann architecture]].

In this system, '''[[computer storage|memory]]''' is a sequence of numbered cells, each containing a small piece of information. The information may be an [[instruction]] to tell the computer what to do. The cell may contain [[data]] that the computer needs to perform the instruction. Any cell may contain either, and indeed what is at one time data might be instructions later.

In general, the contents of a memory cell can be changed at any time - it is a scratchpad rather than a stone tablet.