International standards are technical standards developed by international standards organizations. International standards are available for use worldwide; the most prominent organization is the International Organization for Standardization. International standards may be used either by direct application or by a process of modifying an international standard to suit local conditions; the adoption of international standards results in the creation of equivalent, national standards that are the same as international standards in technical content, but may have editorial differences as to appearance, use of symbols and measurement units, substitution of a point for a comma as the decimal marker, differences resulting from conflicts in governmental regulations or industry-specific requirements caused by fundamental climatic, technological, or infrastructural factors, or the stringency of safety requirements that a given standard authority considers appropriate. International standards are one way of overcoming technical barriers in international commerce caused by differences among technical regulations and standards developed independently and separately by each nation, national standards organization, or company.
Technical barriers arise when different groups come together, each with a large user base, doing some well established thing that between them is mutually incompatible. Establishing international standards is one way of preventing or overcoming this problem; the implementation of standards in industry and commerce became important with the onset of the Industrial Revolution and the need for high-precision machine tools and interchangeable parts. Henry Maudslay developed the first industrially practical screw-cutting lathe in 1800, which allowed for the standardisation of screw thread sizes for the first time. Maudslay's work, as well as the contributions of other engineers, accomplished a modest amount of industry standardization. Joseph Whitworth's screw thread measurements were adopted as the first national standard by companies around the country in 1841, it came to be known as the British Standard Whitworth, was adopted in other countries. By the end of the 19th century differences in standards between companies were making trade difficult and strained.
The Engineering Standards Committee was established in London in 1901 as the world's first national standards body. After the First World War, similar national bodies were established in other countries; the Deutsches Institut für Normung was set up in Germany in 1917, followed by its counterparts, the American National Standard Institute and the French Commission Permanente de Standardisation, both in 1918. By the mid to late 19th century, efforts were being made to standardize electrical measurement. An important figure was R. E. B. Crompton, who became concerned by the large range of different standards and systems used by electrical engineering companies and scientists in the early 20th century. Many companies had entered the market in the 1890s and all chose their own settings for voltage, frequency and the symbols used on circuit diagrams. Adjacent buildings would have incompatible electrical systems because they had been fitted out by different companies. Crompton could see the lack of efficiency in this system and began to consider proposals for an international standard for electric engineering.
In 1904, Crompton represented Britain at the Louisiana Purchase Exposition in St. Louis as part of a delegation by the Institute of Electrical Engineers, he presented a paper on standardisation, so well received that he was asked to look into the formation of a commission to oversee the process. By 1906 his work was complete and he drew up a permanent constitution for the first international standards organization, the International Electrotechnical Commission; the body held its first meeting that year with representatives from 14 countries. In honour of his contribution to electrical standardisation, Lord Kelvin was elected as the body's first President; the International Federation of the National Standardizing Associations was founded in 1926 with a broader remit to enhance international cooperation for all technical standards and specifications. The body was suspended in 1942 during World War II. After the war, ISA was approached by the formed United Nations Standards Coordinating Committee with a proposal to form a new global standards body.
In October 1946, ISA and UNSCC delegates from 25 countries met in London and agreed to join forces to create the new International Organization for Standardization. List of international common standards List of technical standard organisations
A computer program is a collection of instructions that performs a specific task when executed by a computer. A computer requires programs to function. A computer program is written by a computer programmer in a programming language. From the program in its human-readable form of source code, a compiler can derive machine code—a form consisting of instructions that the computer can directly execute. Alternatively, a computer program may be executed with the aid of an interpreter. A collection of computer programs and related data are referred to as software. Computer programs may be categorized along functional lines, such as application software and system software; the underlying method used for some calculation or manipulation is known as an algorithm. The earliest programmable machines preceded the invention of the digital computer. In 1801, Joseph-Marie Jacquard devised a loom that would weave a pattern by following a series of perforated cards. Patterns could be repeated by arranging the cards.
In 1837, Charles Babbage was inspired by Jacquard's loom to attempt to build the Analytical Engine. The names of the components of the calculating device were borrowed from the textile industry. In the textile industry, yarn was brought from the store to be milled; the device would have had a "store"—memory to hold 1,000 numbers of 40 decimal digits each. Numbers from the "store" would have been transferred to the "mill", for processing, and a "thread" being the execution of programmed instructions by the device. It was programmed using two sets of perforated cards—one to direct the operation and the other for the input variables. However, after more than 17,000 pounds of the British government's money, the thousands of cogged wheels and gears never worked together. During a nine-month period in 1842–43, Ada Lovelace translated the memoir of Italian mathematician Luigi Menabrea; the memoir covered the Analytical Engine. The translation contained Note G which detailed a method for calculating Bernoulli numbers using the Analytical Engine.
This note is recognized by some historians as the world's first written computer program. In 1936, Alan Turing introduced the Universal Turing machine—a theoretical device that can model every computation that can be performed on a Turing complete computing machine, it is a finite-state machine. The machine can move the tape forth, changing its contents as it performs an algorithm; the machine starts in the initial state, goes through a sequence of steps, halts when it encounters the halt state. This machine is considered by some to be the origin of the stored-program computer—used by John von Neumann for the "Electronic Computing Instrument" that now bears the von Neumann architecture name; the Z3 computer, invented by Konrad Zuse in Germany, was a programmable computer. A digital computer uses electricity as the calculating component; the Z3 contained 2,400 relays to create the circuits. The circuits provided a floating-point, nine-instruction computer. Programming the Z3 was through a specially designed keyboard and punched tape.
The Electronic Numerical Integrator And Computer was a Turing complete, general-purpose computer that used 17,468 vacuum tubes to create the circuits. At its core, it was a series of Pascalines wired together, its 40 units weighed 30 tons, occupied 1,800 square feet, consumed $650 per hour in electricity when idle. It had 20 base-10 accumulators. Programming the ENIAC took up to two months. Three function tables needed to be rolled to fixed function panels. Function tables were connected to function panels using heavy black cables; each function table had 728 rotating knobs. Programming the ENIAC involved setting some of the 3,000 switches. Debugging a program took a week; the programmers of the ENIAC were women who were known collectively as the "ENIAC girls." The ENIAC featured parallel operations. Different sets of accumulators could work on different algorithms, it used punched card machines for input and output, it was controlled with a clock signal. It ran for eight years, calculating hydrogen bomb parameters, predicting weather patterns, producing firing tables to aim artillery guns.
The Manchester Baby was a stored-program computer. Programming transitioned away from setting dials. Only three bits of memory were available to store each instruction, so it was limited to eight instructions. 32 switches were available for programming. Computers manufactured; the computer program was written on paper for reference. An instruction was represented by a configuration of on/off settings. After setting the configuration, an execute button was pressed; this process was repeated. Computer programs were manually input via paper tape or punched cards. After the medium was loaded, the starting address was set via switches and the execute button pressed. In 1961, the Burroughs B5000 was built to be programmed in the ALGOL 60 language; the hardware featured circuits to ease the compile phase. In 1964, the IBM System/360 was a line of six computers each having the same instruction set architecture; the Model 30 was the least expensive. Customers could retain the same application software; each System/360 model featured multiprogramming.
With operating system support, multiple programs could be in memory at once. When one was waiting for input/output, another could compute; each model could emulate other computers. Customers could upgrade to the System/360 and ret
C++ is a general-purpose programming language, developed by Bjarne Stroustrup as an extension of the C language, or "C with Classes". It has imperative, object-oriented and generic programming features, while providing facilities for low-level memory manipulation, it is always implemented as a compiled language, many vendors provide C++ compilers, including the Free Software Foundation, Intel, IBM, so it is available on many platforms. C++ was designed with a bias toward system programming and embedded, resource-constrained software and large systems, with performance and flexibility of use as its design highlights. C++ has been found useful in many other contexts, with key strengths being software infrastructure and resource-constrained applications, including desktop applications and performance-critical applications. C++ is standardized by the International Organization for Standardization, with the latest standard version ratified and published by ISO in December 2017 as ISO/IEC 14882:2017.
The C++ programming language was standardized in 1998 as ISO/IEC 14882:1998, amended by the C++03, C++11 and C++14 standards. The current C++ 17 standard supersedes these with an enlarged standard library. Before the initial standardization in 1998, C++ was developed by Danish computer scientist Bjarne Stroustrup at Bell Labs since 1979 as an extension of the C language. C++20 is the next planned standard, keeping with the current trend of a new version every three years. In 1979, Bjarne Stroustrup, a Danish computer scientist, began work on "C with Classes", the predecessor to C++; the motivation for creating a new language originated from Stroustrup's experience in programming for his Ph. D. thesis. Stroustrup found that Simula had features that were helpful for large software development, but the language was too slow for practical use, while BCPL was fast but too low-level to be suitable for large software development; when Stroustrup started working in AT&T Bell Labs, he had the problem of analyzing the UNIX kernel with respect to distributed computing.
Remembering his Ph. D. experience, Stroustrup set out to enhance the C language with Simula-like features. C was chosen because it was general-purpose, fast and used; as well as C and Simula's influences, other languages influenced C++, including ALGOL 68, Ada, CLU and ML. Stroustrup's "C with Classes" added features to the C compiler, including classes, derived classes, strong typing and default arguments. In 1983, "C with Classes" was renamed to "C++", adding new features that included virtual functions, function name and operator overloading, constants, type-safe free-store memory allocation, improved type checking, BCPL style single-line comments with two forward slashes. Furthermore, it included the development of a standalone compiler for Cfront. In 1985, the first edition of The C++ Programming Language was released, which became the definitive reference for the language, as there was not yet an official standard; the first commercial implementation of C++ was released in October of the same year.
In 1989, C++ 2.0 was released, followed by the updated second edition of The C++ Programming Language in 1991. New features in 2.0 included multiple inheritance, abstract classes, static member functions, const member functions, protected members. In 1990, The Annotated C++ Reference Manual was published; this work became the basis for the future standard. Feature additions included templates, namespaces, new casts, a boolean type. After the 2.0 update, C++ evolved slowly until, in 2011, the C++11 standard was released, adding numerous new features, enlarging the standard library further, providing more facilities to C++ programmers. After a minor C++14 update released in December 2014, various new additions were introduced in C++17, further changes planned for 2020; as of 2017, C++ remains the third most popular programming language, behind Java and C. On January 3, 2018, Stroustrup was announced as the 2018 winner of the Charles Stark Draper Prize for Engineering, "for conceptualizing and developing the C++ programming language".
According to Stroustrup: "the name signifies the evolutionary nature of the changes from C". This name is credited to Rick Mascitti and was first used in December 1983; when Mascitti was questioned informally in 1992 about the naming, he indicated that it was given in a tongue-in-cheek spirit. The name comes from C's ++ operator and a common naming convention of using "+" to indicate an enhanced computer program. During C++'s development period, the language had been referred to as "new C" and "C with Classes" before acquiring its final name. Throughout C++'s life, its development and evolution has been guided by a set of principles: It must be driven by actual problems and its features should be useful in real world programs; every feature should be implementable. Programmers should be free to pick their own programming style, that style should be supported by C++. Allowing a useful feature is more important than preventing every possible misuse of C++, it should provide facilities for organising programs into separate, well-defined parts, provide facilities for combining separately developed parts.
No implicit violations of the type system (but allow explicit violations.