Interoperability is a characteristic of a product or system, whose interfaces are understood, to work with other products or systems, at present or in the future, in either implementation or access, without any restrictions. While the term was defined for information technology or systems engineering services to allow for information exchange, a broader definition takes into account social and organizational factors that impact system to system performance. Task of building coherent services for users when the individual components are technically different and managed by different organizations If two or more systems are capable of communicating with each other, they exhibit syntactic interoperability when using specified data formats and communication protocols. XML or SQL standards are among the tools of syntactic interoperability; this is true for lower-level data formats, such as ensuring alphabetical characters are stored in a same variation of ASCII or a Unicode format in all the communicating systems.
Beyond the ability of two or more computer systems to exchange information, semantic interoperability is the ability to automatically interpret the information exchanged meaningfully and in order to produce useful results as defined by the end users of both systems. To achieve semantic interoperability, both sides must refer to a common information exchange reference model; the content of the information exchange requests are unambiguously defined: what is sent is the same as what is understood. The possibility of promoting this result by user-driven convergence of disparate interpretations of the same information has been object of study by research prototypes such as S3DB. Cross-domain interoperability involves multiple social, political, legal entities working together for a common interest and/or information exchange. Interoperability imply Open standards ab-initio, i.e. by definition. Interoperability imply exchanges between a range of products, or similar products from several different vendors, or between past and future revisions of the same product.
Interoperability may be developed post-facto, as a special measure between two products, while excluding the rest, by using Open standards. When a vendor is forced to adapt its system to a dominant system, not based on Open standards, it is not interoperability but only compatibility. Open standards rely on a broadly consultative and inclusive group including representatives from vendors and others holding a stake in the development that discusses and debates the technical and economic merits and feasibility of a proposed common protocol. After the doubts and reservations of all members are addressed, the resulting common document is endorsed as a common standard; this document is subsequently released to the public, henceforth becomes an open standard. It is published and is available or at a nominal cost to any and all comers, with no further encumbrances. Various vendors and individuals can use the standards document to make products that implement the common protocol defined in the standard, are thus interoperable by design, with no specific liability or advantage for any customer for choosing one product over another on the basis of standardised features.
The vendors' products compete on the quality of their implementation, user interface, ease of use, price, a host of other factors, while keeping the customers data intact and transferable if he chooses to switch to another competing product for business reasons. Post facto interoperability may be the result of the absolute market dominance of a particular product in contravention of any applicable standards, or if any effective standards were not present at the time of that product's introduction; the vendor behind that product can choose to ignore any forthcoming standards and not co-operate in any standardisation process at all, using its near-monopoly to insist that its product sets the de facto standard by its market dominance. This is not a problem if the product's implementation is open and minimally encumbered, but it may as well be both closed and encumbered; because of the network effect, achieving interoperability with such a product is both critical for any other vendor if it wishes to remain relevant in the market, difficult to accomplish because of lack of co-operation on equal terms with the original vendor, who may well see the new vendor as a potential competitor and threat.
The newer implementations rely on clean-room reverse engineering in the absence of technical data to achieve interoperability. The original vendors can provide such technical data to others in the name of'encouraging competition,' but such data is invariably encumbered, may be of limited use. Availability of such data is not equivalent to an open standard, because: The data is provided by the original vendor on a discretionary basis, who has every interest in blocking the effective implementation of competing solutions, may subtly alter or change its product in newer revisions, so that competitors' implementations are but not quite interoperable, leading customers to consider them unreliable or of a lower quality; these changes can either not be passed on to other vendors at all, or passed on after a strategic delay, maintaining the market dominance of the original vendor. The data itself may be encumbered, e.g. by patents or pricing, leading to a dependence of all competing solutions on the original vendor, leading a revenue stream from the competitors' customers back to the original vendor.
This revenue stream is only a result of the origina
Simplified Chinese characters
Simplified Chinese characters are standardized Chinese characters prescribed in the Table of General Standard Chinese Characters for use in mainland China. Along with traditional Chinese characters, they are one of the two standard character sets of the contemporary Chinese written language; the government of the People's Republic of China in mainland China has promoted them for use in printing since the 1950s and 1960s to encourage literacy. They are used in the People's Republic of China and Singapore. Traditional Chinese characters are used in Hong Kong and the Republic of China. While traditional characters can still be read and understood by many mainland Chinese and the Chinese community in Malaysia and Singapore, these groups retain their use of simplified characters. Overseas Chinese communities tend to use traditional characters. Simplified Chinese characters may be referred to by their official name colloquially; the latter refers to simplifications of character "structure" or "body", character forms that have existed for thousands of years alongside regular, more complicated forms.
On the other hand, the official name refers to the modern systematically simplified character set, which includes not only structural simplification but substantial reduction in the total number of standardized Chinese characters. Simplified character forms were created by reducing the number of strokes and simplifying the forms of a sizable proportion of Chinese characters; some simplifications were based on popular cursive forms embodying graphic or phonetic simplifications of the traditional forms. Some characters were simplified by applying regular rules, for example, by replacing all occurrences of a certain component with a simplified version of the component. Variant characters with the same pronunciation and identical meaning were reduced to a single standardized character the simplest amongst all variants in form. Many characters were left untouched by simplification, are thus identical between the traditional and simplified Chinese orthographies; some simplified characters are dissimilar to and unpredictably different from traditional characters in those where a component is replaced by a simple symbol.
This has led some opponents of simplification to complain that the'overall process' of character simplification is arbitrary. Proponents counter that the system of simplification is internally consistent. Proponents have emphasized a some particular simplified characters as innovative and useful improvements, although many of these have existed for centuries as longstanding and widespread variants. A second round of simplifications was promulgated in 1977, but was retracted in 1986 for a variety of reasons due to the confusion caused and the unpopularity of the second round simplifications. However, the Chinese government never dropped its goal of further simplification in the future. In August 2009, the PRC began collecting public comments for a modified list of simplified characters; the new Table of General Standard Chinese Characters consisting of 8,105 characters was implemented for use by the State Council of the People's Republic of China on June 5, 2013. Although most of the simplified Chinese characters in use today are the result of the works moderated by the government of the People's Republic of China in the 1950s and 60s, character simplification predates the PRC's formation in 1949.
Cursive written text always includes character simplification. Simplified forms used in print are attested as early as the Qin dynasty. One of the earliest proponents of character simplification was Lufei Kui, who proposed in 1909 that simplified characters should be used in education. In the years following the May Fourth Movement in 1919, many anti-imperialist Chinese intellectuals sought ways to modernise China. Traditional culture and values such as Confucianism were challenged. Soon, people in the Movement started to cite the traditional Chinese writing system as an obstacle in modernising China and therefore proposed that a reform be initiated, it was suggested that the Chinese writing system should be either simplified or abolished. Lu Xun, a renowned Chinese author in the 20th century, stated that, "If Chinese characters are not destroyed China will die". Recent commentators have claimed that Chinese characters were blamed for the economic problems in China during that time. In the 1930s and 1940s, discussions on character simplification took place within the Kuomintang government, a large number of Chinese intellectuals and writers maintained that character simplification would help boost literacy in China.
In 1935, 324 simplified characters collected by Qian Xuantong were introduced as the table of first batch of simplified characters, but they were suspended in 1936. The PRC issued its first round of official character simplifications in two documents, the first in 1956 and the second in 1964. Within the PRC, further character simplification became associated with the leftists of the Cultural Revolution, culminating with the second-round simplified characters, which were promulgated in 1977. In part due to the shock and unease felt in the wake of the Cultural Revolution and Mao's death, the second-round of simplifications was poorly received. In 1986 the authorities retracted the second round completely. In the same year, the authorities promulgated a final list of simplifications, identical to the 1964 list except for six changes (including the restoration of three characters, simplified in the First Round: 叠, 覆, 像.
Computer-aided design is the use of computers to aid in the creation, analysis, or optimization of a design. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, to create a database for manufacturing. CAD output is in the form of electronic files for print, machining, or other manufacturing operations; the term CADD is used. Its use in designing electronic systems is known as electronic design automation. In mechanical design it is known as mechanical design automation or computer-aided drafting, which includes the process of creating a technical drawing with the use of computer software. CAD software for mechanical design uses either vector-based graphics to depict the objects of traditional drafting, or may produce raster graphics showing the overall appearance of designed objects. However, it involves more than just shapes; as in the manual drafting of technical and engineering drawings, the output of CAD must convey information, such as materials, processes and tolerances, according to application-specific conventions.
CAD may be used to design figures in two-dimensional space. CAD is an important industrial art extensively used in many applications, including automotive and aerospace industries and architectural design and many more. CAD is widely used to produce computer animation for special effects in movies and technical manuals called DCC digital content creation; the modern ubiquity and power of computers means that perfume bottles and shampoo dispensers are designed using techniques unheard of by engineers of the 1960s. Because of its enormous economic importance, CAD has been a major driving force for research in computational geometry, computer graphics, discrete differential geometry; the design of geometric models for object shapes, in particular, is called computer-aided geometric design. Starting around the mid 1960s, with the IBM Drafting System, computer-aided design systems began to provide more capability than just an ability to reproduce manual drafting with electronic drafting, the cost-benefit for companies to switch to CAD became apparent.
The benefits of CAD systems over manual drafting are the capabilities one takes for granted from computer systems today. CAD provided the designer with the ability to perform engineering calculations. During this transition, calculations were still performed either by hand or by those individuals who could run computer programs. CAD was a revolutionary change in the engineering industry, where draftsmen and engineering roles begin to merge, it did not eliminate departments, as much as it merged departments and empowered draftsman and engineers. CAD is an example of the pervasive effect. Current computer-aided design software packages range from 2D vector-based drafting systems to 3D solid and surface modelers. Modern CAD packages can frequently allow rotations in three dimensions, allowing viewing of a designed object from any desired angle from the inside looking out; some CAD software is capable of dynamic mathematical modeling. CAD technology is used in the design of tools and machinery and in the drafting and design of all types of buildings, from small residential types to the largest commercial and industrial structures.
CAD is used for detailed engineering of 3D models or 2D drawings of physical components, but it is used throughout the engineering process from conceptual design and layout of products, through strength and dynamic analysis of assemblies to definition of manufacturing methods of components. It can be used to design objects such as jewelry, appliances, etc. Furthermore, many CAD applications now offer advanced rendering and animation capabilities so engineers can better visualize their product designs. 4D BIM is a type of virtual construction engineering simulation incorporating time or schedule related information for project management. CAD has become an important technology within the scope of computer-aided technologies, with benefits such as lower product development costs and a shortened design cycle. CAD enables designers to layout and develop work on screen, print it out and save it for future editing, saving time on their drawings. Computer-aided design is one of the many tools used by engineers and designers and is used in many ways depending on the profession of the user and the type of software in question.
CAD is one part of the whole digital product development activity within the product lifecycle management processes, as such is used together with other tools, which are either integrated modules or stand-alone products, such as: Computer-aided engineering and finite element analysis Computer-aided manufacturing including instructions to computer numerical control machines Photorealistic rendering and motion simulation. Document management and revision control using product data management. CAD is used for the accurate creation of photo simulations that are required in the preparation of environmental impact reports, in which computer-aided designs of intended buildings are superimposed into photographs of existing environments to represent what that locale will be like, where the proposed facilities are allowed to be built. Pote
A minicomputer, or colloquially mini, is a class of smaller computers, developed in the mid-1960s and sold for much less than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, The New York Times suggested a consensus definition of a minicomputer as a machine costing less than US$25,000, with an input-output device such as a teleprinter and at least four thousand words of memory, capable of running programs in a higher level language, such as Fortran or BASIC; the class formed a distinct group with its own software architectures and operating systems. Minis were designed for control, human interaction, communication switching as distinct from calculation and record keeping. Many were sold indirectly to original equipment manufacturers for final end use application. During the two decade lifetime of the minicomputer class 100 companies formed and only a half dozen remained; when single-chip CPU microprocessors appeared, beginning with the Intel 4004 in 1971, the term "minicomputer" came to mean a machine that lies in the middle range of the computing spectrum, in between the smallest mainframe computers and the microcomputers.
The term "minicomputer" is little used today. The term "minicomputer" developed in the 1960s to describe the smaller computers that became possible with the use of transistors and core memory technologies, minimal instructions sets and less expensive peripherals such as the ubiquitous Teletype Model 33 ASR, they took up one or a few 19-inch rack cabinets, compared with the large mainframes that could fill a room. The definition of minicomputer is vague with the consequence that there are a number of candidates for the first minicomputer. An early and successful minicomputer was Digital Equipment Corporation's 12-bit PDP-8, built using discrete transistors and cost from US$16,000 upwards when launched in 1964. Versions of the PDP-8 took advantage of small-scale integrated circuits; the important precursors of the PDP-8 include the PDP-5, LINC, the TX-0, the TX-2, the PDP-1. DEC gave rise to a number of minicomputer companies along Massachusetts Route 128, including Data General, Wang Laboratories, Apollo Computer, Prime Computer.
Minicomputers were known as midrange computers. They grew to have high processing power and capacity, they were used in manufacturing process control, telephone switching and to control laboratory equipment. In the 1970s, they were the hardware, used to launch the computer-aided design industry and other similar industries where a smaller dedicated system was needed; the 7400 series of TTL integrated circuits started appearing in minicomputers in the late 1960s. The 74181 arithmetic logic unit was used in the CPU data paths; each 74181 had a bus width of hence the popularity of bit-slice architecture. Some scientific computers, such as the Nicolet 1080, would use the 7400 series in groups of five ICs for their uncommon twenty bits architecture; the 7400 series offered data-selectors, three-state buffers, etc. in dual in-line packages with one-tenth inch spacing, making major system components and architecture evident to the naked eye. Starting in the 1980s, many minicomputers used VLSI circuits.
At the launch of the MITS Altair 8800 in 1975, Radio Electronics magazine referred to the system as a "minicomputer", although the term microcomputer soon became usual for personal computers based on single-chip microprocessors. At the time, microcomputers were 8-bit single-user simple machines running simple program-launcher operating systems like CP/M or MS-DOS, while minis were much more powerful systems that ran full multi-user, multitasking operating systems, such as VMS and Unix, although the classical mini was a 16-bit computer, the emerging higher performance superminis were 32-bit; the decline of the minis happened due to the lower cost of microprocessor-based hardware, the emergence of inexpensive and deployable local area network systems, the emergence of the 68020, 80286 and the 80386 microprocessors, the desire of end-users to be less reliant on inflexible minicomputer manufacturers and IT departments or "data centers". The result was that minicomputers and computer terminals were replaced by networked workstations, file servers and PCs in some installations, beginning in the latter half of the 1980s.
During the 1990s, the change from minicomputers to inexpensive PC networks was cemented by the development of several versions of Unix and Unix-like systems that ran on the Intel x86 microprocessor architecture, including Solaris, FreeBSD, NetBSD and OpenBSD. The Microsoft Windows series of operating systems, beginning with, now included server versions that supported preemptive multitasking and other features required for servers; as microprocessors have become more powerful, the CPUs built up from multiple components – once the distinguishing feature differentiating mainframes and midrange systems from microcomputers – have become obsolete in the largest mainframe computers. Digital Equipment Corporation was once the leading minicomputer manufacturer, at one time the second-largest computer company after IBM, but as the minicomputer declined in the face of generic Unix servers and Intel-based PCs, not only DEC, but every other minicomputer company including Data General, Computervision and Wang Laboratories, many based in New England collapsed or merg
Traditional Chinese characters
Traditional Chinese characters are Chinese characters in any character set that does not contain newly created characters or character substitutions performed after 1946. They are most the characters in the standardized character sets of Taiwan, of Hong Kong and Macau, in the Kangxi Dictionary; the modern shapes of traditional Chinese characters first appeared with the emergence of the clerical script during the Han Dynasty, have been more or less stable since the 5th century. The retronym "traditional Chinese" is used to contrast traditional characters with Simplified Chinese characters, a standardized character set introduced by the government of the People's Republic of China on Mainland China in the 1950s. Traditional Chinese characters are used in Taiwan, Hong Kong, Macau. In contrast, Simplified Chinese characters are used in mainland China and Malaysia in official publications. However, several countries – such as Australia, the US and Canada – are increasing their number of printed materials in Simplified Chinese, to better accommodate citizens from mainland China.
The debate on traditional and simplified Chinese characters has been a long-running issue among Chinese communities. A large number of overseas Chinese online newspapers allow users to switch between both character sets. Although simplified characters are taught and endorsed by the government of China, there is no prohibition against the use of traditional characters. Traditional characters are used informally in regions in China in handwriting and used for inscriptions and religious text, they are retained in logos or graphics to evoke yesteryear. Nonetheless, the vast majority of media and communications in China is dominated by simplified characters. In Hong Kong and Macau, Traditional Chinese has been the legal written form since colonial times. In recent years, simplified Chinese characters in Hong Kong and Macau has appeared to accommodate Mainland Chinese tourists and immigrants; this has led to concerns by many residents to protect their local heritage. Taiwan has never adopted simplified characters.
The use of simplified characters in official documents is prohibited by the government of Taiwan. Simplified characters are understood to a certain extent by any educated Taiwanese, learning to read them takes little effort; some stroke simplifications that have been incorporated into Simplified Chinese are in common use in handwriting. For example, while the name of Taiwan is written as 臺灣, the semi-simplified name 台灣 is acceptable to write in official documents. In Southeast Asia, the Chinese Filipino community continues to be one of the most conservative regarding simplification. While major public universities are teaching simplified characters, many well-established Chinese schools still use traditional characters. Publications like the Chinese Commercial News, World News, United Daily News still use traditional characters. On the other hand, the Philippine Chinese Daily uses simplified. Aside from local newspapers, magazines from Hong Kong, such as the Yazhou Zhoukan, are found in some bookstores.
In case of film or television subtitles on DVD, the Chinese dub, used in Philippines is the same as the one used in Taiwan. This is because the DVDs belongs to DVD Region Code 3. Hence, most of the subtitles are in Traditional Characters. Overseas Chinese in the United States have long used traditional characters. A major influx of Chinese immigrants to the United States occurred during the latter half of the 19th century, before the standardization of simplified characters. Therefore, United States public notices and signage in Chinese are in Traditional Chinese. Traditional Chinese characters are called several different names within the Chinese-speaking world; the government of Taiwan calls traditional Chinese characters standard characters or orthodox characters. However, the same term is used outside Taiwan to distinguish standard and traditional characters from variant and idiomatic characters. In contrast, users of traditional characters outside Taiwan, such as those in Hong Kong and overseas Chinese communities, users of simplified Chinese characters, call them complex characters.
An informal name sometimes used by users of simplified characters is "old characters". Users of traditional characters sometimes refer them as "Full Chinese characters" to distinguish them from simplified Chinese characters; some traditional character users argue that traditional characters are the original form of the Chinese characters and cannot be called "complex". Simplified characters cannot be "standard" because they are not used in all Chinese-speaking regions. Conversely, supporters of simplified Chinese characters object to the description of traditional characters as "standard," since they view the new simplified characters as the contemporary standard used by the vast majority of Chinese speakers, they point out that traditional characters are not traditional as many Chinese characters have been made more elaborate over time. Some people refer to traditional characters as "proper characters" and modernized characters as "simplified-stroke characters" (sim
Google Play is a digital distribution service operated and developed by Google LLC. It serves as the official app store for the Android operating system, allowing users to browse and download applications developed with the Android software development kit and published through Google. Google Play serves as a digital media store, offering music, books and television programs, it offered Google hardware devices for purchase until the introduction of a separate online hardware retailer, Google Store, on March 11, 2015, it offered news publications and magazines before the revamp of Google News in May 15, 2018. Applications are available through Google Play either free of charge or at a cost, they can be downloaded directly on an Android device through the Play Store mobile app or by deploying the application to a device from the Google Play website. Applications exploiting hardware capabilities of a device can be targeted to users of devices with specific hardware components, such as a motion sensor or a front-facing camera.
The Google Play store had over 82 billion app downloads in 2016 and has reached over 3.5 million apps published in 2017. It has been the subject of multiple issues concerning security, in which malicious software has been approved and uploaded to the store and downloaded by users, with varying degrees of severity. Google Play was launched on March 6, 2012, bringing together the Android Market, Google Music, the Google eBookstore under one brand, marking a shift in Google's digital distribution strategy; the services included in the Google Play are Google Play Books, Google Play Games, Google Play Movies & TV, Google Play Music. Following their re-branding, Google has expanded the geographical support for each of the services; as of 2017, Google Play features over 3.5 million Android applications. Users in over 145 countries can purchase apps, although Google notes on its support pages that "Paid content may not be available in some provinces or territories if the governing country is listed above."
Developers in over 150 locations can distribute apps on Google Play, though not every location supports merchant registration. To distribute apps, developers have to pay a one-time $25 registration fee for a Google Play Developer Console account. App developers can control which countries an app is distributed to, as well as the pricing for the app and in-app purchases in each country. Developers receive 70% of the application price, while the remaining 30% goes to the distribution partner and operating fees. Developers can set up sales, with the original price struck out and a banner underneath informing users when the sale ends. Google Play allows developers to release early versions of apps to a select group of users, as alpha or beta tests. Developers can release apps through staged rollouts, in which "your update reaches only a percentage of your users, which you can increase over time." Users can pre-order select apps to have the items delivered as soon. Some network carriers offer billing for Google Play purchases, allowing users to opt for charges in the monthly phone bill rather than on credit cards.
Users can request refunds within 48 hours after a purchase if "something you bought isn't working, isn't what you expected, was bought by accident, or you changed your mind about the purchase". Apps meeting specific usability requirements can qualify as a Wear OS app. Google Play Games is an online gaming service for Android that features real-time multiplayer gaming capabilities, cloud saves and public leaderboards, achievements; the service was introduced at the Google I/O 2013 Developer Conference, the standalone mobile app was launched on July 24, 2013. Google Play Music is online music locker, it features over 40 million songs, gives users free cloud storage of up to 50,000 songs. As of May 2017, Google Play Music is available in 64 countries. Google Play Books is an ebook digital distribution service. Google Play offers over five million ebooks available for purchase, users can upload up to 1,000 of their own ebooks in the form of PDF or EPUB file formats; as of January 2017, Google Play Books is available in 75 countries.
Google Play Books can be found on the archive.org website available for readers and for download. Google Play Movies & TV is a video on demand service offering movies and television shows available for purchase or rental, depending on availability; as of January 2017, movies are available in over 110 countries, while TV shows are available only in Australia, Canada, Germany, Switzerland, the United States and the United Kingdom. Google Play Newsstand is a news aggregator and digital newsstand service offering subscriptions to digital magazines and topical news feeds; as of January 2017, the basic Newsstand service, with topical news feeds, is available worldwide. Paid Newsstand content is available in over 35 countries. In May 15, 2018, the mobile app merged with Google Weather to form Google News; the Newsstand section continued to appear on the Google Play website until November 5, 2018. Google Play, before March 2015, had a Devices section for users to purchase Google Nexus devices, Chromecasts, other Google-branded hardware, accessories.
A separate online hardware retailer called the Google Store was introduced on March 11, 2015, replacing the Devices section of Google Play. Google Play originated from three distinct products: Android Market, Google Music and Google eBookstore; the Android Market was announced by Google on August 28, 2008, was mad
Technical drawing, drafting or drawing, is the act and discipline of composing drawings that visually communicate how something functions or is constructed. Technical drawing is essential for communicating ideas in engineering. To make the drawings easier to understand, people use familiar symbols, units of measurement, notation systems, visual styles, page layout. Together, such conventions constitute a visual language and help to ensure that the drawing is unambiguous and easy to understand. Many of the symbols and principles of technical drawing are codified in an international standard called ISO 128; the need for precise communication in the preparation of a functional document distinguishes technical drawing from the expressive drawing of the visual arts. Artistic drawings are subjectively interpreted. Technical drawings are understood to have one intended meaning. A drafter, draftsperson, or draughtsman is a person. A professional drafter who makes technical drawings is sometimes called a drafting technician.
A sketch is a executed, freehand drawing, not intended as a finished work. In general, sketching is a quick way to record an idea for use. Architect's sketches serve as a way to try out different ideas and establish a composition before a more finished work when the finished work is expensive and time-consuming. Architectural sketches, for example, are a kind of diagrams; these sketches, like metaphors, are used by architects as a means of communication in aiding design collaboration. This tool helps architects to abstract attributes of hypothetical provisional design solutions and summarize their complex patterns, hereby enhancing the design process. Italic text The basic drafting procedure is to place a piece of paper on a smooth surface with right-angle corners and straight sides—typically a drawing board. A sliding straightedge known as a T-square is placed on one of the sides, allowing it to be slid across the side of the table, over the surface of the paper. "Parallel lines" can be drawn by moving the T-square and running a pencil or technical pen along the T-square's edge.
The T-square is used to hold other devices such as set triangles. In this case, the drafter places one or more triangles of known angles on the T-square—which is itself at right angles to the edge of the table—and can draw lines at any chosen angle to others on the page. Modern drafting tables come equipped with a drafting machine, supported on both sides of the table to slide over a large piece of paper; because it is secured on both sides, lines drawn along the edge are guaranteed to be parallel. In addition, the drafter uses several technical drawing tools to draw circles. Primary among these are the compasses, used for drawing simple arcs and circles, the French curve, for drawing curves. A spline is a rubber coated articulated metal. Drafting templates assist the drafter with creating recurring objects in a drawing without having to reproduce the object from scratch every time; this is useful when using common symbols. Templates are sold commercially by a number of vendors customized to a specific task, but it is not uncommon for a drafter to create his own templates.
This basic drafting system requires an accurate table and constant attention to the positioning of the tools. A common error is to allow the triangles to push the top of the T-square down thereby throwing off all angles. Tasks as simple as drawing two angled lines meeting at a point require a number of moves of the T-square and triangles, in general, drafting can be a time-consuming process. A solution to these problems was the introduction of the mechanical "drafting machine", an application of the pantograph which allowed the drafter to have an accurate right angle at any point on the page quite quickly; these machines included the ability to change the angle, thereby removing the need for the triangles as well. In addition to the mastery of the mechanics of drawing lines and circles onto a piece of paper—with respect to the detailing of physical objects—the drafting effort requires a thorough understanding of geometry and spatial comprehension, in all cases demands precision and accuracy, attention to detail of high order.
Although drafting is sometimes accomplished by a project engineer, architect, or shop personnel, skilled drafters accomplish the task, are always in demand to some degree. Today, the mechanics of the drafting task have been automated and accelerated through the use of computer-aided design systems. There are two types of computer-aided design systems used for the production of technical drawings" two dimensions and three dimensions. 2D CAD systems such as AutoCAD or MicroStation replace the paper drawing discipline. The lines, circles and curves are created within the software, it is down to the technical drawing skill of the user to produce the drawing. There is still much scope for error in the drawing when producing first and third angle orthographic projections, auxiliary projections and cross sections. A 2D CAD system is an electronic drawing board, its greatest strength over direct to paper technical drawing is in the making of revisions. Whereas in a conventional hand dr