1.
JavaScript
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JavaScript is a high-level, dynamic, untyped, and interpreted programming language. It has been standardized in the ECMAScript language specification, JavaScript is prototype-based with first-class functions, making it a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles. JavaScript was influenced by programming languages such as Self and Scheme, JavaScript is also used in environments that are not Web-based, such as PDF documents, site-specific browsers, and desktop widgets. Newer and faster JavaScript virtual machines and platforms built upon them have increased the popularity of JavaScript for server-side Web applications. On the client side, developers have traditionally implemented JavaScript as an interpreted language, programmers also use JavaScript in video-game development, in crafting desktop and mobile applications, and in server-side network programming with run-time environments such as Node. js. In 1994, a company called Mosaic Communications was founded in Mountain View, California, however, it intentionally shared no code with NCSA Mosaic. The internal codename for the browser was Mozilla, which stood for Mosaic killer. The first version of the Web browser, Mosaic Netscape 0.9, was released in late 1994, within four months it had already taken three-quarters of the browser market and became the main browser for Internet in the 1990s. To avoid trademark problems with the NCSA, the browser was subsequently renamed Netscape Navigator in the same year. Netscape Communications realized that the Web needed to more dynamic. In 1995, the company recruited Brendan Eich with the goal of embedding the Scheme programming language into its Netscape Navigator, to defend the idea of JavaScript against competing proposals, the company needed a prototype. Eich wrote one in 10 days, in May 1995, there is a common misconception that JavaScript was influenced by an earlier Web page scripting language developed by Nombas named C--. Brendan Eich, however, had never heard of C-- before he created LiveScript, Nombas did pitch their embedded Web page scripting to Netscape, though Web page scripting was not a new concept, as shown by the ViolaWWW Web browser. Nombas later switched to offering JavaScript instead of C-- in their ScriptEase product and was part of the TC39 group that standardized ECMAScript, in December 1995, soon after releasing JavaScript for browsers, Netscape introduced an implementation of the language for server-side scripting with Netscape Enterprise Server. Since the mid-2000s, additional server-side JavaScript implementations have been introduced, Microsoft script technologies including VBScript and JScript were released in 1996. JScript, an implementation of Netscapes JavaScript, was part of Internet Explorer 3. JScript was also available for server-side scripting in Internet Information Server, JavaScript began to acquire a reputation for being one of the roadblocks to a cross-platform and standards-driven Web. Some developers took on the task of trying to make their sites work in both major browsers, but many could not afford the time
2.
Software developer
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A software developer is a person concerned with facets of the software development process, including the research, design, programming, and testing of computer software. Other job titles which are used with similar meanings are programmer, software analyst. According to developer Eric Sink, the differences between system design, software development, and programming are more apparent, even more so that developers become systems architects, those who design the multi-leveled architecture or component interactions of a large software system. In a large company, there may be employees whose sole responsibility consists of one of the phases above. In smaller development environments, a few people or even an individual might handle the complete process. The word software was coined as a prank as early as 1953, before this time, computers were programmed either by customers, or the few commercial computer vendors of the time, such as UNIVAC and IBM. The first company founded to provide products and services was Computer Usage Company in 1955. The software industry expanded in the early 1960s, almost immediately after computers were first sold in mass-produced quantities, universities, government, and business customers created a demand for software. Many of these programs were written in-house by full-time staff programmers, some were distributed freely between users of a particular machine for no charge. Others were done on a basis, and other firms such as Computer Sciences Corporation started to grow. The computer/hardware makers started bundling operating systems, systems software and programming environments with their machines, new software was built for microcomputers, so other manufacturers including IBM, followed DECs example quickly, resulting in the IBM AS/400 amongst others. The industry expanded greatly with the rise of the computer in the mid-1970s. In the following years, it created a growing market for games, applications. DOS, Microsofts first operating system product, was the dominant operating system at the time, by 2014 the role of cloud developer had been defined, in this context, one definition of a developer in general was published, Developers make software for the world to use. The job of a developer is to crank out code -- fresh code for new products, code fixes for maintenance, code for business logic, bus factor Software Developer description from the US Department of Labor
3.
James Gosling
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James Arthur Gosling, OC is a Canadian computer scientist, best known as the creator of the Java programming language. James Gosling received a Bachelor of Science from the University of Calgary and his M. A. while working towards his doctorate, he wrote a version of Emacs called Gosling Emacs. Before joining Sun Microsystems he built a version of Unix for a 16-way computer system while at Carnegie Mellon University. There, he developed several compilers and mail systems. Between 1984 and 2010, Gosling was with Sun Microsystems and he is known as the father of the Java programming language. He got the idea for the Java VM while writing a program to port software from a PERQ by translating Perq Q-Code to VAX assembler, on April 2,2010, Gosling left Sun Microsystems which had recently been acquired by the Oracle Corporation. Regarding why he left, Gosling cited reductions in pay, status, decision-making ability, change of role, later, during the Oracle v Google trial over Android, he clarified his position saying While I have differences with Oracle, in this case they are in the right. We were all really disturbed, even Jonathan, he just decided to put on a face and tried to turn lemons into lemonade. However, he approved of the ruling that APIs should not be copyrightable. On March 28,2011, James Gosling announced on his blog that he had hired by Google. Five months later, he announced that he joined a startup called Liquid Robotics, Gosling is listed as an adviser at the Scala company Typesafe Inc. Independent Director at Jelastic and Strategic Advisor for Eucalyptus, Gosling is known for his love of proving the unknown and has noted that his favorite irrational number is √2. He has a picture of the first 1,000 digits of √2 in his office. Gosling initially became known as the author of Gosling Emacs, and also invented the windowing system NeWS and he is generally credited with having invented the Java programming language in 1994. He created the design of Java and implemented the languages original compiler. Pascal compiled into p-code to foster precisely this kind of portability, for his achievement the National Academy of Engineering in the United States elected him as a Foreign Associate member. Another contribution of Goslings was co-writing the bundle program, a utility thoroughly detailed in Brian Kernighan,2002, he was awarded The Economist Innovation Award. 2002, he was awarded The Flame Award USENIX Lifetime Achievement Award,2007, he was made an Officer of the Order of Canada
4.
Sun Microsystems
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Sun contributed significantly to the evolution of several key computing technologies, among them Unix, RISC processors, thin client computing, and virtualized computing. Sun was founded on February 24,1982, at its height, the Sun headquarters were in Santa Clara, California, on the former west campus of the Agnews Developmental Center. On January 27,2010, Oracle Corporation acquired Sun by for US$7.4 billion, other technologies include the Java platform, MySQL, and NFS. Sun was a proponent of open systems in general and Unix in particular, the initial design for what became Suns first Unix workstation, the Sun-1, was conceived by Andy Bechtolsheim when he was a graduate student at Stanford University in Palo Alto, California. Bechtolsheim originally designed the SUN workstation for the Stanford University Network communications project as a personal CAD workstation and it was designed around the Motorola 68000 processor with an advanced memory management unit to support the Unix operating system with virtual memory support. He built the first ones from spare parts obtained from Stanfords Department of Computer Science, on February 24,1982, Vinod Khosla, Andy Bechtolsheim, and Scott McNealy, all Stanford graduate students, founded Sun Microsystems. Bill Joy of Berkeley, a developer of the Berkeley Software Distribution. The Sun name is derived from the initials of the Stanford University Network, Sun was profitable from its first quarter in July 1982. By 1983 Sun was known for producing 68000-based systems with high-quality graphics that were the only computers other than DECs VAX to run 4. 2BSD and it licensed the computer design to other manufacturers, which typically used it to build Multibus-based systems running Unix from UniSoft. Suns initial public offering was in 1986 under the stock symbol SUNW, the symbol was changed in 2007 to JAVA, Sun stated that the brand awareness associated with its Java platform better represented the companys current strategy. Suns logo, which features four interleaved copies of the sun in the form of a rotationally symmetric ambigram, was designed by professor Vaughan Pratt. The initial version of the logo was orange and had the sides oriented horizontally and vertically, but it was rotated to stand on one corner and re-colored purple. In the dot-com bubble, Sun began making more money. It also began spending more, hiring workers and building itself out. Some of this was because of demand, but much was from web start-up companies anticipating business that would never happen. Sales in Suns important hardware division went into free-fall as customers closed shop, several quarters of steep losses led to executive departures, rounds of layoffs, and other cost cutting. In December 2001, the fell to the 1998, pre-bubble level of about $100. But it kept falling, faster than many other tech companies, a year later it had dipped below $10 but bounced back to $20
5.
Oracle Corporation
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Oracle Corporation is a multinational computer technology corporation, headquartered in Redwood Shores, California. In 2015 Oracle was the second-largest software maker by revenue, after Microsoft, larry Ellison co-founded Oracle Corporation in 1977 with Bob Miner and Ed Oates under the name Software Development Laboratories. Ellison took inspiration from the 1970 paper written by Edgar F. Codd on relational database management systems named A Relational Model of Data for Large Shared Data Banks and he heard about the IBM System R database from an article in the IBM Research Journal provided by Oates. Also derived from Codds theories, Ellison wanted to make Oracles product compatible with System R, SDL changed its name to Relational Software, Inc in 1979, then again to Oracle Systems Corporation in 1982, to align itself more closely with its flagship product Oracle Database. At this stage Bob Miner served as the senior programmer. In 1995, Oracle Systems Corporation changed its name to Oracle Corporation, officially named Oracle, but sometimes referred to as Oracle Corporation, part of Oracle Corporations early success arose from using the C programming language to implement its products. This eased porting to different operating systems, many of the products have been added to Oracles portfolio through acquisitions. Oracles E-delivery service provides generic downloadable Oracle software and documentation, Oracle Database Release 10, In 2004, Oracle Corporation shipped release 10g as the then latest version of Oracle Database. Release 11, Release 11g became the current Oracle Database version in 2007, Oracle Corporation released Oracle Database 11g Release 2 in September 2009. This version was available in four commercial editions—Enterprise Edition, Standard Edition, Standard Edition One, the licensing of these editions shows various restrictions and obligations that are considered complex. The Enterprise Edition, the most expensive of the Database Editions, has the fewest restrictions —, Oracle Corporation constrains the Standard Edition and Standard Edition One with more licensing restrictions, in accordance with their lower price. Release 12, Release 12c became available on July 1,2013, Oracle acquired Rdb in 1994 from Digital Equipment Corporation. Oracle has since made many enhancements to product and development continues as of 2008. Released in 2008, the Oracle Beehive collaboration software provides team workspaces, email, calendar, instant messaging, customers can use Beehive as licensed software or as software as a service. Oracle also sells a suite of business applications, users can access these facilities through a browser interface over the Internet or via a corporate intranet. The Social Engagement and Monitoring cloud provides the most effective and efficient responses across social, SEM is able to route correct responses to the right team, member, or customer-experience channel to ensure the best customer service. The analysis helps vendors to understand what is important to customers and it identifies trends, spikes, and anomalies to make real-time course corrections. It also can identify brand advocates, the SEM cloud identifies customer intention and interests by analyzing the common ways customers talk about a product or a service
6.
Software release life cycle
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Usage of the alpha/beta test terminology originated at IBM. As long ago as the 1950s, IBM used similar terminology for their hardware development, a test was the verification of a new product before public announcement. B test was the verification before releasing the product to be manufactured, C test was the final test before general availability of the product. Martin Belsky, a manager on some of IBMs earlier software projects claimed to have invented the terminology, IBM dropped the alpha/beta terminology during the 1960s, but by then it had received fairly wide notice. The usage of beta test to refer to testing done by customers was not done in IBM, rather, IBM used the term field test. Pre-alpha refers to all activities performed during the project before formal testing. These activities can include requirements analysis, software design, software development, in typical open source development, there are several types of pre-alpha versions. Milestone versions include specific sets of functions and are released as soon as the functionality is complete, the alpha phase of the release life cycle is the first phase to begin software testing. In this phase, developers generally test the software using white-box techniques, additional validation is then performed using black-box or gray-box techniques, by another testing team. Moving to black-box testing inside the organization is known as alpha release, alpha software can be unstable and could cause crashes or data loss. Alpha software may not contain all of the features that are planned for the final version, in general, external availability of alpha software is uncommon in proprietary software, while open source software often has publicly available alpha versions. The alpha phase usually ends with a freeze, indicating that no more features will be added to the software. At this time, the software is said to be feature complete, Beta, named after the second letter of the Greek alphabet, is the software development phase following alpha. Software in the stage is also known as betaware. Beta phase generally begins when the software is complete but likely to contain a number of known or unknown bugs. Software in the phase will generally have many more bugs in it than completed software, as well as speed/performance issues. The focus of beta testing is reducing impacts to users, often incorporating usability testing, the process of delivering a beta version to the users is called beta release and this is typically the first time that the software is available outside of the organization that developed it. Beta version software is useful for demonstrations and previews within an organization
7.
C++
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C++ is a general-purpose programming language. It has imperative, object-oriented and generic programming features, while also providing facilities for low-level memory manipulation and it was designed with a bias toward system programming and embedded, resource-constrained and large systems, with performance, efficiency and flexibility of use as its design highlights. C++ is a language, with implementations of it available on many platforms and provided by various organizations, including the Free Software Foundation, LLVM, Microsoft, Intel. C++ is standardized by the International Organization for Standardization, with the latest standard version ratified and published by ISO in December 2014 as ISO/IEC14882,2014. The C++ programming language was standardized in 1998 as ISO/IEC14882,1998. The current C++14 standard supersedes these and C++11, with new features, the C++17 standard is due in 2017, with the draft largely implemented by some compilers already, and C++20 is the next planned standard thereafter. Many other programming languages have influenced by C++, including C#, D, Java. In 1979, Bjarne Stroustrup, a Danish computer scientist, began work on C with Classes, the motivation for creating a new language originated from Stroustrups experience in programming for his Ph. D. thesis. 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, portable, as well as C and Simulas influences, other languages also influenced C++, including ALGOL68, Ada, CLU and ML. Initially, Stroustrups C with Classes added features to the C compiler, Cpre, including classes, derived classes, strong typing, inlining, furthermore, it included the development of a standalone compiler for C++, Cfront. In 1985, the first edition of The C++ Programming Language was released, the first commercial implementation of C++ was released in October of the same year. In 1989, C++2.0 was released, followed by the second edition of The C++ Programming Language in 1991. New features in 2.0 included multiple inheritance, abstract classes, static functions, const member functions. In 1990, The Annotated C++ Reference Manual was published and this work became the basis for the future standard. Later feature additions included templates, exceptions, namespaces, new casts, after a minor C++14 update released in December 2014, various new additions are planned for 2017 and 2020. According to Stroustrup, the name signifies the 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
8.
Operating system
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An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is Microsoft Windows with a market share of around 83. 3%. MacOS by Apple Inc. is in place, and the varieties of Linux is in third position. Linux distributions are dominant in the server and supercomputing sectors, other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can run one program at a time. Multi-tasking may be characterized in preemptive and co-operative types, in preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e. g. Solaris, Linux, cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking, 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem, a distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing, distributed computations are carried out on more than one machine. When computers in a work in cooperation, they form a distributed system. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses, embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy and they are able to operate with a limited number of resources. They are very compact and extremely efficient by design, Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is a system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could run different programs in succession to speed up processing
9.
Microsoft Windows
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Microsoft Windows is a metafamily of graphical operating systems developed, marketed, and sold by Microsoft. It consists of families of operating systems, each of which cater to a certain sector of the computing industry with the OS typically associated with IBM PC compatible architecture. Active Windows families include Windows NT, Windows Embedded and Windows Phone, defunct Windows families include Windows 9x, Windows 10 Mobile is an active product, unrelated to the defunct family Windows Mobile. Microsoft introduced an operating environment named Windows on November 20,1985, Microsoft Windows came to dominate the worlds personal computer market with over 90% market share, overtaking Mac OS, which had been introduced in 1984. Apple came to see Windows as an encroachment on their innovation in GUI development as implemented on products such as the Lisa. On PCs, Windows is still the most popular operating system, however, in 2014, Microsoft admitted losing the majority of the overall operating system market to Android, because of the massive growth in sales of Android smartphones. In 2014, the number of Windows devices sold was less than 25% that of Android devices sold and this comparison however may not be fully relevant, as the two operating systems traditionally target different platforms. As of September 2016, the most recent version of Windows for PCs, tablets, smartphones, the most recent versions for server computers is Windows Server 2016. A specialized version of Windows runs on the Xbox One game console, Microsoft, the developer of Windows, has registered several trademarks each of which denote a family of Windows operating systems that target a specific sector of the computing industry. It now consists of three operating system subfamilies that are released almost at the time and share the same kernel. Windows, The operating system for personal computers, tablets. The latest version is Windows 10, the main competitor of this family is macOS by Apple Inc. for personal computers and Android for mobile devices. Windows Server, The operating system for server computers, the latest version is Windows Server 2016. Unlike its clients sibling, it has adopted a strong naming scheme, the main competitor of this family is Linux. Windows PE, A lightweight version of its Windows sibling meant to operate as an operating system, used for installing Windows on bare-metal computers. The latest version is Windows PE10.0.10586.0, Windows Embedded, Initially, Microsoft developed Windows CE as a general-purpose operating system for every device that was too resource-limited to be called a full-fledged computer. The following Windows families are no longer being developed, Windows 9x, Microsoft now caters to the consumers market with Windows NT. Windows Mobile, The predecessor to Windows Phone, it was a mobile operating system
10.
Solaris (operating system)
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Solaris is a Unix operating system originally developed by Sun Microsystems. It superseded their earlier SunOS in 1993, Oracle Solaris, so named as of 2010, has been owned by Oracle Corporation since the Sun acquisition by Oracle in January 2010. Solaris is known for its scalability, especially on SPARC systems, Solaris supports SPARC-based and x86-based workstations and servers from Oracle and other vendors, with efforts underway to port to additional platforms. Solaris is registered as compliant with the Single Unix Specification, historically, Solaris was developed as proprietary software. In June 2005, Sun Microsystems released most of the codebase under the CDDL license, with OpenSolaris, Sun wanted to build a developer and user community around the software. After the acquisition of Sun Microsystems in January 2010, Oracle decided to discontinue the OpenSolaris distribution, in August 2010, Oracle discontinued providing public updates to the source code of the Solaris kernel, effectively turning Solaris 11 back into a closed source proprietary operating system. Following that, in 2011 the Solaris 11 kernel source code leaked to BitTorrent, however, through the Oracle Technology Network, industry partners can still gain access to the in-development Solaris source code. Source code for the source components of Solaris 11 is available for download from Oracle. In 1987, AT&T Corporation and Sun announced that they were collaborating on a project to merge the most popular Unix variants on the market at that time, BSD, System V and this became Unix System V Release 4. On September 4,1991, Sun announced that it would replace its existing BSD-derived Unix, SunOS4 and this was identified internally as SunOS5, but a new marketing name was introduced at the same time, Solaris 2. The justification for this new overbrand was that it encompassed not only SunOS, but also the OpenWindows graphical user interface and Open Network Computing functionality. Although SunOS4.1. x micro releases were retroactively named Solaris 1 by Sun, for releases based on SunOS5, the SunOS minor version is included in the Solaris release number. For example, Solaris 2.4 incorporates SunOS5.4. After Solaris 2.6, the 2. was dropped from the name, so Solaris 7 incorporates SunOS5.7. Although SunSoft stated in its initial Solaris 2 press release their intent to support both SPARC and x86 systems, the first two Solaris 2 releases,2.0 and 2.1, were SPARC-only. An x86 version of Solaris 2.1 was released in June 1993, about 6 months after the SPARC version, as a desktop and it included the Wabi emulator to support Windows applications. At the time, Sun also offered the Interactive Unix system that it had acquired from Interactive Systems Corporation, in 1994, Sun released Solaris 2.4, supporting both SPARC and x86 systems from a unified source code base. Solaris uses a code base for the platforms it supports, SPARC
11.
Linux
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Linux is a Unix-like computer operating system assembled under the model of free and open-source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released on September 17,1991 by Linus Torvalds, the Free Software Foundation uses the name GNU/Linux to describe the operating system, which has led to some controversy. Linux was originally developed for computers based on the Intel x86 architecture. Because of the dominance of Android on smartphones, Linux has the largest installed base of all operating systems. Linux is also the operating system on servers and other big iron systems such as mainframe computers. It is used by around 2. 3% of desktop computers, the Chromebook, which runs on Chrome OS, dominates the US K–12 education market and represents nearly 20% of the sub-$300 notebook sales in the US. Linux also runs on embedded systems – devices whose operating system is built into the firmware and is highly tailored to the system. This includes TiVo and similar DVR devices, network routers, facility automation controls, televisions, many smartphones and tablet computers run Android and other Linux derivatives. The development of Linux is one of the most prominent examples of free, the underlying source code may be used, modified and distributed—commercially or non-commercially—by anyone under the terms of its respective licenses, such as the GNU General Public License. Typically, Linux is packaged in a known as a Linux distribution for both desktop and server use. Distributions intended to run on servers may omit all graphical environments from the standard install, because Linux is freely redistributable, anyone may create a distribution for any intended use. The Unix operating system was conceived and implemented in 1969 at AT&Ts Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, first released in 1971, Unix was written entirely in assembly language, as was common practice at the time. Later, in a key pioneering approach in 1973, it was rewritten in the C programming language by Dennis Ritchie, the availability of a high-level language implementation of Unix made its porting to different computer platforms easier. Due to an earlier antitrust case forbidding it from entering the computer business, as a result, Unix grew quickly and became widely adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs, freed of the legal obligation requiring free licensing, the GNU Project, started in 1983 by Richard Stallman, has the goal of creating a complete Unix-compatible software system composed entirely of free software. Later, in 1985, Stallman started the Free Software Foundation, by the early 1990s, many of the programs required in an operating system were completed, although low-level elements such as device drivers, daemons, and the kernel were stalled and incomplete. Linus Torvalds has stated that if the GNU kernel had been available at the time, although not released until 1992 due to legal complications, development of 386BSD, from which NetBSD, OpenBSD and FreeBSD descended, predated that of Linux. Torvalds has also stated that if 386BSD had been available at the time, although the complete source code of MINIX was freely available, the licensing terms prevented it from being free software until the licensing changed in April 2000
12.
MacOS
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Within the market of desktop, laptop and home computers, and by web usage, it is the second most widely used desktop OS after Microsoft Windows. Launched in 2001 as Mac OS X, the series is the latest in the family of Macintosh operating systems, Mac OS X succeeded classic Mac OS, which was introduced in 1984, and the final release of which was Mac OS9 in 1999. An initial, early version of the system, Mac OS X Server 1.0, was released in 1999, the first desktop version, Mac OS X10.0, followed in March 2001. In 2012, Apple rebranded Mac OS X to OS X. Releases were code named after big cats from the release up until OS X10.8 Mountain Lion. Beginning in 2013 with OS X10.9 Mavericks, releases have been named after landmarks in California, in 2016, Apple rebranded OS X to macOS, adopting the nomenclature that it uses for their other operating systems, iOS, watchOS, and tvOS. The latest version of macOS is macOS10.12 Sierra, macOS is based on technologies developed at NeXT between 1985 and 1997, when Apple acquired the company. The X in Mac OS X and OS X is pronounced ten, macOS shares its Unix-based core, named Darwin, and many of its frameworks with iOS, tvOS and watchOS. A heavily modified version of Mac OS X10.4 Tiger was used for the first-generation Apple TV, Apple also used to have a separate line of releases of Mac OS X designed for servers. Beginning with Mac OS X10.7 Lion, the functions were made available as a separate package on the Mac App Store. Releases of Mac OS X from 1999 to 2005 can run only on the PowerPC-based Macs from the time period, Mac OS X10.5 Leopard was released as a Universal binary, meaning the installer disc supported both Intel and PowerPC processors. In 2009, Apple released Mac OS X10.6 Snow Leopard, in 2011, Apple released Mac OS X10.7 Lion, which no longer supported 32-bit Intel processors and also did not include Rosetta. All versions of the system released since then run exclusively on 64-bit Intel CPUs, the heritage of what would become macOS had originated at NeXT, a company founded by Steve Jobs following his departure from Apple in 1985. There, the Unix-like NeXTSTEP operating system was developed, and then launched in 1989 and its graphical user interface was built on top of an object-oriented GUI toolkit using the Objective-C programming language. This led Apple to purchase NeXT in 1996, allowing NeXTSTEP, then called OPENSTEP, previous Macintosh operating systems were named using Arabic numerals, e. g. Mac OS8 and Mac OS9. The letter X in Mac OS Xs name refers to the number 10 and it is therefore correctly pronounced ten /ˈtɛn/ in this context. However, a common mispronunciation is X /ˈɛks/, consumer releases of Mac OS X included more backward compatibility. Mac OS applications could be rewritten to run natively via the Carbon API, the consumer version of Mac OS X was launched in 2001 with Mac OS X10.0. Reviews were variable, with praise for its sophisticated, glossy Aqua interface
13.
Computing platform
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Computing platform means in general sense, where any piece of software is executed. It may be the hardware or the system, even a web browser or other application. The term computing platform can refer to different abstraction levels, including a hardware architecture, an operating system. In total it can be said to be the stage on which programs can run. For example, an OS may be a platform that abstracts the underlying differences in hardware, platforms may also include, Hardware alone, in the case of small embedded systems. Embedded systems can access hardware directly, without an OS, this is referred to as running on bare metal, a browser in the case of web-based software. The browser itself runs on a platform, but this is not relevant to software running within the browser. An application, such as a spreadsheet or word processor, which hosts software written in a scripting language. This can be extended to writing fully-fledged applications with the Microsoft Office suite as a platform, software frameworks that provide ready-made functionality. Cloud computing and Platform as a Service, the social networking sites Twitter and facebook are also considered development platforms. A virtual machine such as the Java virtual machine, applications are compiled into a format similar to machine code, known as bytecode, which is then executed by the VM. A virtualized version of a system, including virtualized hardware, OS, software. These allow, for instance, a typical Windows program to run on what is physically a Mac, some architectures have multiple layers, with each layer acting as a platform to the one above it. In general, a component only has to be adapted to the layer immediately beneath it, however, the JVM, the layer beneath the application, does have to be built separately for each OS
14.
X86-64
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X86-64 is the 64-bit version of the x86 instruction set. It supports vastly larger amounts of memory and physical memory than is possible on its 32-bit predecessors. X86-64 also provides 64-bit general-purpose registers and numerous other enhancements and it is fully backward compatible with 16-bit and 32-bit x86 code. The original specification, created by AMD and released in 2000, has been implemented by AMD, Intel, the AMD K8 processor was the first to implement the architecture, this was the first significant addition to the x86 architecture designed by a company other than Intel. Intel was forced to suit and introduced a modified NetBurst family which was fully software-compatible with AMDs design. VIA Technologies introduced x86-64 in their VIA Isaiah architecture, with the VIA Nano, the x86-64 specification is distinct from the Intel Itanium architecture, which is not compatible on the native instruction set level with the x86 architecture. AMD64 was created as an alternative to the radically different IA-64 architecture, the first AMD64-based processor, the Opteron, was released in April 2003. AMDs processors implementing the AMD64 architecture include Opteron, Athlon 64, Athlon 64 X2, Athlon 64 FX, Athlon II, Turion 64, Turion 64 X2, Sempron, Phenom, Phenom II, FX, Fusion and Ryzen. The primary defining characteristic of AMD64 is the availability of 64-bit general-purpose processor registers, 64-bit integer arithmetic and logical operations, the designers took the opportunity to make other improvements as well. Some of the most significant changes are described below, pushes and pops on the stack default to 8-byte strides, and pointers are 8 bytes wide. Additional registers In addition to increasing the size of the general-purpose registers, AMD64 still has fewer registers than many common RISC instruction sets or VLIW-like machines such as the IA-64. However, an AMD64 implementation may have far more internal registers than the number of architectural registers exposed by the instruction set, additional XMM registers Similarly, the number of 128-bit XMM registers is also increased from 8 to 16. Larger virtual address space The AMD64 architecture defines a 64-bit virtual address format and this allows up to 256 TB of virtual address space. The architecture definition allows this limit to be raised in future implementations to the full 64 bits and this is compared to just 4 GB for the x86. This means that very large files can be operated on by mapping the entire file into the address space, rather than having to map regions of the file into. Larger physical address space The original implementation of the AMD64 architecture implemented 40-bit physical addresses, current implementations of the AMD64 architecture extend this to 48-bit physical addresses and therefore can address up to 256 TB of RAM. The architecture permits extending this to 52 bits in the future, for comparison, 32-bit x86 processors are limited to 64 GB of RAM in Physical Address Extension mode, or 4 GB of RAM without PAE mode. Any implementation therefore allows the physical address limit as under long mode
15.
ARM architecture
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ARM, originally Acorn RISC Machine, later Advanced RISC Machine, is a family of reduced instruction set computing architectures for computer processors, configured for various environments. It also designs cores that implement this instruction set and licenses these designs to a number of companies that incorporate those core designs into their own products, a RISC-based computer design approach means processors require fewer transistors than typical complex instruction set computing x86 processors in most personal computers. This approach reduces costs, heat and power use and these characteristics are desirable for light, portable, battery-powered devices—including smartphones, laptops and tablet computers, and other embedded systems. For supercomputers, which large amounts of electricity, ARM could also be a power-efficient solution. ARM Holdings periodically releases updates to architectures and core designs, some older cores can also provide hardware execution of Java bytecodes. The ARMv8-A architecture, announced in October 2011, adds support for a 64-bit address space, with over 100 billion ARM processors produced as of 2017, ARM is the most widely used instruction set architecture in terms of quantity produced. Currently, the widely used Cortex cores, older classic cores, the British computer manufacturer Acorn Computers first developed the Acorn RISC Machine architecture in the 1980s to use in its personal computers. Its first ARM-based products were coprocessor modules for the BBC Micro series of computers, according to Sophie Wilson, all the tested processors at that time performed about the same, with about a 4 Mbit/second bandwidth. After testing all available processors and finding them lacking, Acorn decided it needed a new architecture, inspired by white papers on the Berkeley RISC project, Acorn considered designing its own processor. Wilson developed the set, writing a simulation of the processor in BBC BASIC that ran on a BBC Micro with a 6502 second processor. This convinced Acorn engineers they were on the right track, Wilson approached Acorns CEO, Hermann Hauser, and requested more resources. Hauser gave his approval and assembled a team to implement Wilsons model in hardware. The official Acorn RISC Machine project started in October 1983 and they chose VLSI Technology as the silicon partner, as they were a source of ROMs and custom chips for Acorn. Wilson and Furber led the design and they implemented it with a similar efficiency ethos as the 6502. A key design goal was achieving low-latency input/output handling like the 6502, the 6502s memory access architecture had let developers produce fast machines without costly direct memory access hardware. The first samples of ARM silicon worked properly when first received and tested on 26 April 1985, Wilson subsequently rewrote BBC BASIC in ARM assembly language. The in-depth knowledge gained from designing the instruction set enabled the code to be very dense, the original aim of a principally ARM-based computer was achieved in 1987 with the release of the Acorn Archimedes. In 1992, Acorn once more won the Queens Award for Technology for the ARM, the ARM2 featured a 32-bit data bus, 26-bit address space and 27 32-bit registers
16.
SPARC
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The Scalable Processor Architecture is a reduced instruction set computing instruction set architecture originally developed by Sun Microsystems. Since the establishment of SPARC International, Inc. in 1989, SPARC International is also responsible for licensing and promoting the SPARC architecture, managing SPARC trademarks, and providing conformance testing. As a result of SPARC International, SPARC is fully open, non-proprietary, later, SPARC processors were used in SMP and CC-NUMA servers produced by Sun, Solbourne and Fujitsu, among others, and designed for 64-bit operation. As of July 2016, the latest commercial high-end SPARC processors are Fujitsus SPARC64 X+ and SPARC64 XIfx, the SPARC architecture was heavily influenced by the earlier RISC designs including the RISC I and II from the University of California, Berkeley and the IBM801. These original RISC designs were minimalist, including as few features or op-codes as possible and this made them similar to the MIPS architecture in many ways, including the lack of instructions such as multiply or divide. Another feature of SPARC influenced by this early RISC movement is the delay slot. The SPARC processor usually contains as many as 160 general purpose registers, according to the Oracle SPARC Architecture 2015 specification an implementation may contain from 72 to 640 general-purpose 64-bit registers. At any point, only 32 of them are visible to software –8 are a set of global registers. These 24 registers form what is called a window, and at function call/return. Each window has 8 local registers and shares 8 registers with each of the adjacent windows, the shared registers are used for passing function parameters and returning values, and the local registers are used for retaining local values across function calls. Other architectures that include similar register file features include Intel i960, IA-64, the architecture has gone through several revisions. It gained hardware multiply and divide functionality in Version 8, 64-bit were added to the version 9 SPARC specification published in 1994. In SPARC Version 8, the floating point register file has 16 double precision registers, each of them can be used as two single precision registers, providing a total of 32 single precision registers. An odd-even number pair of double precision registers can be used as a quad precision register, SPARC Version 9 added 16 more double precision registers, but these additional registers can not be accessed as single precision registers. No SPARC CPU implements quad-precision operations in hardware as of 2004, tagged add and subtract instructions perform adds and subtracts on values checking that the bottom two bits of both operands are 0 and reporting overflow if they are not. This can be useful in the implementation of the run time for ML, Lisp, the endianness of the 32-bit SPARC V8 architecture is purely big-endian. The latter is used for accessing data from inherently little-endian devices. There have been three revisions of the architecture
17.
Software license
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A software license is a legal instrument governing the use or redistribution of software. Under United States copyright law all software is copyright protected, in code as also object code form. The only exception is software in the public domain, most distributed software can be categorized according to its license type. Two common categories for software under copyright law, and therefore with licenses which grant the licensee specific rights, are proprietary software and free, unlicensed software outside the copyright protection is either public domain software or software which is non-distributed, non-licensed and handled as internal business trade secret. Contrary to popular belief, distributed unlicensed software is copyright protected. Examples for this are unauthorized software leaks or software projects which are placed on public software repositories like GitHub without specified license. As voluntarily handing software into the domain is problematic in some international law domains, there are also licenses granting PD-like rights. Therefore, the owner of a copy of software is legally entitled to use that copy of software. Hence, if the end-user of software is the owner of the respective copy, as many proprietary licenses only enumerate the rights that the user already has under 17 U. S. C. §117, and yet proclaim to take away from the user. Proprietary software licenses often proclaim to give software publishers more control over the way their software is used by keeping ownership of each copy of software with the software publisher. The form of the relationship if it is a lease or a purchase, for example UMG v. Augusto or Vernor v. Autodesk. The ownership of goods, like software applications and video games, is challenged by licensed. The Swiss based company UsedSoft innovated the resale of business software and this feature of proprietary software licenses means that certain rights regarding the software are reserved by the software publisher. Therefore, it is typical of EULAs to include terms which define the uses of the software, the most significant effect of this form of licensing is that, if ownership of the software remains with the software publisher, then the end-user must accept the software license. In other words, without acceptance of the license, the end-user may not use the software at all, one example of such a proprietary software license is the license for Microsoft Windows. The most common licensing models are per single user or per user in the appropriate volume discount level, Licensing per concurrent/floating user also occurs, where all users in a network have access to the program, but only a specific number at the same time. Another license model is licensing per dongle which allows the owner of the dongle to use the program on any computer, Licensing per server, CPU or points, regardless the number of users, is common practice as well as site or company licenses
18.
Open-source software
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Open-source software may be developed in a collaborative public manner. According to scientists who studied it, open-source software is a prominent example of open collaboration, a 2008 report by the Standish Group states that adoption of open-source software models has resulted in savings of about $60 billion per year to consumers. In the early days of computing, programmers and developers shared software in order to learn from each other, eventually the open source notion moved to the way side of commercialization of software in the years 1970-1980. In 1997, Eric Raymond published The Cathedral and the Bazaar and this source code subsequently became the basis behind SeaMonkey, Mozilla Firefox, Thunderbird and KompoZer. Netscapes act prompted Raymond and others to look into how to bring the Free Software Foundations free software ideas, the new term they chose was open source, which was soon adopted by Bruce Perens, publisher Tim OReilly, Linus Torvalds, and others. The Open Source Initiative was founded in February 1998 to encourage use of the new term, a Microsoft executive publicly stated in 2001 that open source is an intellectual property destroyer. I cant imagine something that could be worse than this for the software business, IBM, Oracle, Google and State Farm are just a few of the companies with a serious public stake in todays competitive open-source market. There has been a significant shift in the corporate philosophy concerning the development of FOSS, the free software movement was launched in 1983. In 1998, a group of individuals advocated that the free software should be replaced by open-source software as an expression which is less ambiguous. Software developers may want to publish their software with an open-source license, the Open Source Definition, notably, presents an open-source philosophy, and further defines the terms of usage, modification and redistribution of open-source software. Software licenses grant rights to users which would otherwise be reserved by law to the copyright holder. Several open-source software licenses have qualified within the boundaries of the Open Source Definition, the open source label came out of a strategy session held on April 7,1998 in Palo Alto in reaction to Netscapes January 1998 announcement of a source code release for Navigator. They used the opportunity before the release of Navigators source code to clarify a potential confusion caused by the ambiguity of the free in English. Many people claimed that the birth of the Internet, since 1969, started the open source movement, the Free Software Foundation, started in 1985, intended the word free to mean freedom to distribute and not freedom from cost. Since a great deal of free software already was free of charge, such software became associated with zero cost. The Open Source Initiative was formed in February 1998 by Eric Raymond and they sought to bring a higher profile to the practical benefits of freely available source code, and they wanted to bring major software businesses and other high-tech industries into open source. Perens attempted to open source as a service mark for the OSI. The Open Source Initiatives definition is recognized by governments internationally as the standard or de facto definition, OSI uses The Open Source Definition to determine whether it considers a software license open source
19.
Application software
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An application program is a computer program designed to perform a group of coordinated functions, tasks, or activities for the benefit of the user. Examples of an application include a processor, a spreadsheet, an accounting application, a web browser, a media player, an aeronautical flight simulator. The collective noun application software refers to all applications collectively and this contrasts with system software, which is mainly involved with running the computer. Applications may be bundled with the computer and its software or published separately. Apps built for mobile platforms are called mobile apps, in information technology, an application is a computer program designed to help people perform an activity. An application thus differs from a system, a utility. Depending on the activity for which it was designed, an application can manipulate text, numbers, graphics, some application packages focus on a single task, such as word processing, others, called integrated software include several applications. User-written software tailors systems to meet the specific needs. User-written software includes templates, word processor macros, scientific simulations, graphics. Even email filters are a kind of user software, users create this software themselves and often overlook how important it is. The delineation between system software such as operating systems and application software is not exact, however, and is occasionally the object of controversy. As another example, the GNU/Linux naming controversy is, in part, the above definitions may exclude some applications that may exist on some computers in large organizations. For an alternative definition of an app, see Application Portfolio Management, the word application, once used as an adjective, is not restricted to the of or pertaining to application software meaning. Sometimes a new and popular application arises which only runs on one platform and this is called a killer application or killer app. There are many different ways to divide up different types of application software, web apps have indeed greatly increased in popularity for some uses, but the advantages of applications make them unlikely to disappear soon, if ever. Furthermore, the two can be complementary, and even integrated, Application software can also be seen as being either horizontal or vertical. Horizontal applications are more popular and widespread, because they are general purpose, vertical applications are niche products, designed for a particular type of industry or business, or department within an organization. Integrated suites of software will try to handle every aspect possible of, for example, manufacturing or banking systems, or accounting
20.
Embedded system
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An embedded system is a computer system with a dedicated function within a larger mechanical or electrical system, often with real-time computing constraints. It is embedded as part of a device often including hardware. Embedded systems control many devices in use today. Ninety-eight percent of all microprocessors are manufactured as components of embedded systems, examples of properties of typically embedded computers when compared with general-purpose counterparts are low power consumption, small size, rugged operating ranges, and low per-unit cost. This comes at the price of limited processing resources, which make them more difficult to program. For example, intelligent techniques can be designed to power consumption of embedded systems. Modern embedded systems are based on microcontrollers, but ordinary microprocessors are also common. In either case, the processor used may be ranging from general purpose to those specialised in certain class of computations. A common standard class of dedicated processors is the signal processor. Since the embedded system is dedicated to tasks, design engineers can optimize it to reduce the size and cost of the product and increase the reliability. Some embedded systems are mass-produced, benefiting from economies of scale, complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or enclosure. One of the very first recognizably modern embedded systems was the Apollo Guidance Computer, an early mass-produced embedded system was the Autonetics D-17 guidance computer for the Minuteman missile, released in 1961. When the Minuteman II went into production in 1966, the D-17 was replaced with a new computer that was the first high-volume use of integrated circuits. Since these early applications in the 1960s, embedded systems have come down in price and there has been a rise in processing power. An early microprocessor for example, the Intel 4004, was designed for calculators and other systems but still required external memory. By the early 1980s, memory, input and output system components had been integrated into the chip as the processor forming a microcontroller. Microcontrollers find applications where a computer would be too costly. A comparatively low-cost microcontroller may be programmed to fulfill the role as a large number of separate components
21.
Mobile phone
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A mobile phone is a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area. The radio frequency link establishes a connection to the systems of a mobile phone operator. Most modern mobile telephone services use a network architecture, and, therefore. Mobile phones which offer these and more general computing capabilities are referred to as smartphones, the first handheld mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing c.4.4 lbs. In 1983, the DynaTAC 8000x was the first commercially available mobile phone. From 1983 to 2014, worldwide mobile phone subscriptions grew to seven billion, penetrating 100% of the global population. In first quarter of 2016, the top smartphone manufacturers were Samsung, Apple, a handheld mobile radio telephone service was envisioned in the early stages of radio engineering. In 1917, Finnish inventor Eric Tigerstedt filed a patent for a pocket-size folding telephone with a thin carbon microphone. Early predecessors of cellular phones included analog radio communications from ships, the race to create truly portable telephone devices began after World War II, with developments taking place in many countries. These 0G systems were not cellular, supported few simultaneous calls, the first handheld mobile phone was demonstrated by John F. Mitchell and Martin Cooper of Motorola in 1973, using a handset weighing c.4.4 lbs. The first commercial automated cellular network was launched in Japan by Nippon Telegraph and this was followed in 1981 by the simultaneous launch of the Nordic Mobile Telephone system in Denmark, Finland, Norway, and Sweden. Several other countries followed in the early to mid-1980s. These first-generation systems could support far more simultaneous calls but still used analog cellular technology, in 1983, the DynaTAC 8000x was the first commercially available handheld mobile phone. In 1991, the digital cellular technology was launched in Finland by Radiolinja on the GSM standard. This sparked competition in the sector as the new operators challenged the incumbent 1G network operators, ten years later, in 2001, the third generation was launched in Japan by NTT DoCoMo on the WCDMA standard. This was followed by 3. 5G, 3G+ or turbo 3G enhancements based on the high-speed packet access family, allowing UMTS networks to have data transfer speeds. By 2009, it had become clear that, at point, 3G networks would be overwhelmed by the growth of bandwidth-intensive applications. Consequently, the industry began looking to data-optimized fourth-generation technologies, with the promise of speed improvements up to ten-fold over existing 3G technologies
22.
Server (computing)
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In computing, a server is a computer program or a device that provides functionality for other programs or devices, called clients. This architecture is called the model, and a single overall computation is distributed across multiple processes or devices. Servers can provide various functionalities, often called services, such as sharing data or resources among multiple clients, a single server can serve multiple clients, and a single client can use multiple servers. A client process may run on the device or may connect over a network to a server on a different device. Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, designating a computer as server-class hardware implies that it is specialized for running servers on it. The use of the server in computing comes from queueing theory, where it dates to the mid 20th century, being notably used in Kendall. In earlier papers, such as the Erlang, more terms such as operators are used. In computing, server dates at least to RFC5, one of the earliest documents describing ARPANET, the use of serving also dates to early documents, such as RFC4, contrasting serving-host with using-host. The Jargon File defines server in the sense of a process performing service for requests, usually remote, with the 1981 version reading. A kind of DAEMON which performs a service for the requester, strictly speaking, the term server refers to a computer program or process. Through metonymy, it refers to a used to running one or several server programs. On a network, such a device is called a host, in addition to server, the words serve and service are frequently used, though servicer and servant are not. The word service may refer to either the form of functionality. Alternatively, it may refer to a program that turns a computer into a server. Originally used as servers serve users, in the sense of obey, today one says that servers serve data. For instance, web servers serve web pages to users or service their requests, the server is part of the client–server model, in this model, a server serves data for clients. The nature of communication between a client and server is request and response and this is in contrast with peer-to-peer model in which the relationship is on-demand reciprocation. In principle, any computerized process that can be used or called by another process is a server, thus any general purpose computer connected to a network can host servers
23.
Supercomputer
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A supercomputer is a computer with a high level of computing performance compared to a general-purpose computer. Performance of a supercomputer is measured in floating-point operations per second instead of instructions per second. As of 2015, there are supercomputers which can perform up to quadrillions of FLOPS and it tops the rankings in the TOP500 supercomputer list. Sunway TaihuLights emergence is also notable for its use of indigenous chips, as of June 2016, China, for the first time, had more computers on the TOP500 list than the United States. However, U. S. built computers held ten of the top 20 positions, in November 2016 the U. S. has five of the top 10, throughout their history, they have been essential in the field of cryptanalysis. The use of multi-core processors combined with centralization is an emerging trend, the history of supercomputing goes back to the 1960s, with the Atlas at the University of Manchester and a series of computers at Control Data Corporation, designed by Seymour Cray. These used innovative designs and parallelism to achieve superior computational peak performance, Cray left CDC in 1972 to form his own company, Cray Research. Four years after leaving CDC, Cray delivered the 80 MHz Cray 1 in 1976, the Cray-2 released in 1985 was an 8 processor liquid cooled computer and Fluorinert was pumped through it as it operated. It performed at 1.9 gigaflops and was the second fastest after M-13 supercomputer in Moscow. Fujitsus Numerical Wind Tunnel supercomputer used 166 vector processors to gain the top spot in 1994 with a speed of 1.7 gigaFLOPS per processor. The Hitachi SR2201 obtained a performance of 600 GFLOPS in 1996 by using 2048 processors connected via a fast three-dimensional crossbar network. The Intel Paragon could have 1000 to 4000 Intel i860 processors in various configurations, the Paragon was a MIMD machine which connected processors via a high speed two dimensional mesh, allowing processes to execute on separate nodes, communicating via the Message Passing Interface. Approaches to supercomputer architecture have taken dramatic turns since the earliest systems were introduced in the 1960s, early supercomputer architectures pioneered by Seymour Cray relied on compact innovative designs and local parallelism to achieve superior computational peak performance. However, in time the demand for increased computational power ushered in the age of massively parallel systems, supercomputers of the 21st century can use over 100,000 processors connected by fast connections. The Connection Machine CM-5 supercomputer is a parallel processing computer capable of many billions of arithmetic operations per second. Throughout the decades, the management of heat density has remained a key issue for most centralized supercomputers, the large amount of heat generated by a system may also have other effects, e. g. reducing the lifetime of other system components. There have been diverse approaches to management, from pumping Fluorinert through the system. Systems with a number of processors generally take one of two paths
24.
Java applet
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A Java applet is a small application which is written in Java or another programming language that compiles to Java bytecode and delivered to users in the form of that bytecode. The user launches the Java applet from a web page, a Java applet can appear in a frame of the web page, a new application window, Suns AppletViewer, or a stand-alone tool for testing applets. Java applets were introduced in the first version of the Java language, Java applets are usually written in Java, but other languages such as Jython, JRuby, Pascal, Scala, or Eiffel may be used as well. Java applets run at very fast speeds and, until 2011, unlike JavaScript, Java applets had access to 3D hardware acceleration, making them well-suited for non-trivial, computation-intensive visualizations. As browsers have gained support for hardware-accelerated graphics thanks to the technology, as well as just-in-time compiled JavaScript. Since Javas bytecode is cross-platform, Java applets can be executed by browsers for many platforms, including Microsoft Windows, FreeBSD, Unix, macOS, Java applet technology has been marked for deprecation. The Applets are used to provide features to web applications that cannot be provided by HTML alone. They can capture mouse input. In response to actions, an applet can change the provided graphic content. This makes applets well-suited for demonstration, visualization, and teaching, there are online applet collections for studying various subjects, from physics to heart physiology. An applet can also be an area only, providing, for instance. If needed, an applet can leave the area and run as a separate window. Applets can also play media in formats that are not natively supported by the browser, pages coded in HTML may embed parameters within them that are passed to the applet. Because of this, the same applet may have a different appearance depending on the parameters that were passed, as applets were available before CSS and DHTML were standard, they were also widely used for trivial effects such as rollover navigation buttons. Heavily criticized, this usage is now declining, Java applets are executed in a sandbox by most web browsers, preventing them from accessing local data like the clipboard or file system. The code of the applet is downloaded from a web server, after which the browser either embeds the applet into a web page or opens a new window showing the user interface. A Java applet extends the class java. applet. Applet, or in the case of a Swing applet, the class which must override methods from the applet class to set up a user interface inside itself is a descendant of Panel which is a descendant of Container. As applet inherits from container, it has largely the same user interface possibilities as an ordinary Java application, the first implementations involved downloading an applet class by class. While classes are small files, there are many of them
25.
HTML
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Hypertext Markup Language is the standard markup language for creating web pages and web applications. With Cascading Style Sheets and JavaScript it forms a triad of cornerstone technologies for the World Wide Web, Web browsers receive HTML documents from a webserver or from local storage and render them into multimedia web pages. HTML describes the structure of a web page semantically and originally included cues for the appearance of the document, HTML elements are the building blocks of HTML pages. With HTML constructs, images and other objects, such as interactive forms and it provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items. HTML elements are delineated by tags, written using angle brackets, tags such as <img /> and <input /> introduce content into the page directly. Include explicit close tags for elements that permit content but are left empty, by carefully following the W3Cs compatibility guidelines, a user agent should be able to interpret the document equally as HTML or XHTML. For documents that are XHTML1.0 and have made compatible in this way. When delivered as XHTML, browsers should use an XML parser, HTML4 defined three different versions of the language, Strict, Transitional and Frameset. The Transitional and Frameset versions allow for presentational markup, which is omitted in the Strict version, instead, cascading style sheets are encouraged to improve the presentation of HTML documents. Because XHTML1 only defines an XML syntax for the language defined by HTML4, as this list demonstrates, the loose versions of the specification are maintained for legacy support. However, contrary to popular misconceptions, the move to XHTML does not imply a removal of this legacy support, rather the X in XML stands for extensible and the W3C is modularizing the entire specification and opening it up to independent extensions. The primary achievement in the move from XHTML1.0 to XHTML1.1 is the modularization of the entire specification, the strict version of HTML is deployed in XHTML1.1 through a set of modular extensions to the base XHTML1.1 specification. Likewise, someone looking for the loose or frameset specifications will find similar extended XHTML1.1 support, the modularization also allows for separate features to develop on their own timetable. So for example, XHTML1.1 will allow quicker migration to emerging XML standards such as MathML, in summary, the HTML4 specification primarily reined in all the various HTML implementations into a single clearly written specification based on SGML. XHTML1.0, ported this specification, as is, next, XHTML1.1 takes advantage of the extensible nature of XML and modularizes the whole specification. XHTML2.0 was intended to be the first step in adding new features to the specification in a standards-body-based approach. The WHATWG considers their work as living standard HTML for what constitutes the state of the art in major browser implementations by Apple, Google, Mozilla, Opera, hTML5 is specified by the HTML Working Group of the W3C following the W3C process. HTML lacks some of the found in earlier hypertext systems, such as source tracking, fat links
26.
Java byte code
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Java bytecode is the instruction set of the Java virtual machine. Each bytecode is composed of one, or in some cases two bytes that represent the instruction, along with zero or more bytes for passing parameters. Of the 256 possible byte-long opcodes, as of 2015,198 are in use,54 are reserved for future use, a Java programmer does not need to be aware of or understand Java bytecode at all. Many instructions have prefixes and/or suffixes referring to the types of operands they operate on and these are as follows, For example, iadd will add two integers, while dadd will add two doubles. The const, load, and store instructions may take a suffix of the form _n. The maximum n for const differs by type, the const instructions push a value of the specified type onto the stack. For example, iconst_5 will push an integer 5, while dconst_1 will push a double 1, there is also an aconst_null, which pushes null. The n for the load and store instructions specifies the location in the table to load from or store to. The aload_0 instruction pushes the object in variable 0 onto the stack, istore_1 stores the integer on the top of the stack into variable 1. For variables with higher numbers the suffix is dropped and operands must be used, some projects provide Java assemblers to enable writing Java bytecode by hand. Assembly code may be generated by machine, for example by a compiler targeting a Java virtual machine. Java syntax is used for class or interface definition, method bodies are specified using bytecode instructions. Krakatau Bytecode Tools, currently contains three tools, a decompiler and disassembler for Java classfiles and an assembler to create classfiles, lilac, an assembler and disassembler for the Java virtual machine. Some processors can execute Java bytecode natively, such processors are termed Java processors. The Java virtual machine provides some support for dynamically typed languages, JSR292 added a new invokedynamic instruction at the JVM level, to allow method invocation relying on dynamic type checking. The Da Vinci Machine is a virtual machine implementation that hosts JVM extensions aimed at supporting dynamic languages. All JVMs supporting JSE7 also include the invokedynamic opcode, the bytecode can be viewed as text using F3
27.
Java virtual machine
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A Java virtual machine is an abstract computing machine that enables a computer to run a Java program. There are three notions of the JVM, specification, implementation, and instance, the specification is a document that formally describes what is required of a JVM implementation. Having a single specification ensures all implementations are interoperable, a JVM implementation is a computer program that meets the requirements of the JVM specification. An instance of a JVM is a running in a process that executes a computer program compiled into Java bytecode. Java Runtime Environment is a package that contains what is required to run a Java program. It includes a Java Virtual Machine implementation together with an implementation of the Java Class Library, the Oracle Corporation, which owns the Java trademark, distributes a Java Runtime environment with their Java Virtual Machine called HotSpot. Java Development Kit is a superset of a JRE and contains tools for Java programmers, the Java Development Kit is provided free of charge either by Oracle Corporation directly, or by the OpenJDK open source project, which is governed by Oracle. The Java virtual machine is an abstract computer defined by a specification, the main reason for this omission is to not unnecessarily constrain implementers. Any Java application can be run only inside some concrete implementation of the specification of the Java virtual machine. Starting with Java Platform, Standard Edition 5.0, changes to the JVM specification have been developed under the Java Community Process as JSR924. As of 2006, changes to specification to support changes proposed to the file format are being done as a maintenance release of JSR924. Oracle provides tests that verify the operation of implementations of the Java Virtual Machine. One of Oracles JVMs is named HotSpot, the other, inherited from BEA Systems is JRockit, clean-room Java implementations include Kaffe and IBM J9. Oracle owns the Java trademark and may allow its use to certify implementation suites as fully compatible with Oracles specification, one of the organizational units of JVM byte code is a class. A class loader implementation must be able to recognize and load anything that conforms to the Java class file format, any implementation is free to recognize other binary forms besides class files, but it must recognize class files. Initialization, invokes Java code that initializes class variables to their proper starting values, in general, there are two types of class loader, bootstrap class loader and user defined class loader. Every Java virtual machine implementation must have a class loader. The Java virtual machine specification doesnt specify how a class loader should locate classes, the JVM has instructions for the following groups of tasks, The aim is binary compatibility
28.
Compiler
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A compiler is a computer program that transforms source code written in a programming language into another computer language, with the latter often having a binary form known as object code. The most common reason for converting source code is to create an executable program, the name compiler is primarily used for programs that translate source code from a high-level programming language to a lower level language. If the compiled program can run on a computer whose CPU or operating system is different from the one on which the compiler runs, more generally, compilers are a specific type of translator. While all programs that take a set of programming specifications and translate them, a program that translates from a low-level language to a higher level one is a decompiler. A program that translates between high-level languages is called a source-to-source compiler or transpiler. A language rewriter is usually a program that translates the form of expressions without a change of language, the term compiler-compiler is sometimes used to refer to a parser generator, a tool often used to help create the lexer and parser. A compiler is likely to many or all of the following operations, lexical analysis, preprocessing, parsing, semantic analysis, code generation. Program faults caused by incorrect compiler behavior can be difficult to track down and work around, therefore. Software for early computers was written in assembly language. The notion of a high level programming language dates back to 1943, no actual implementation occurred until the 1970s, however. The first actual compilers date from the 1950s, identifying the very first is hard, because there is subjectivity in deciding when programs become advanced enough to count as the full concept rather than a precursor. 1952 saw two important advances. Grace Hopper wrote the compiler for the A-0 programming language, though the A-0 functioned more as a loader or linker than the notion of a full compiler. Also in 1952, the first autocode compiler was developed by Alick Glennie for the Mark 1 computer at the University of Manchester and this is considered by some to be the first compiled programming language. The FORTRAN team led by John Backus at IBM is generally credited as having introduced the first unambiguously complete compiler, COBOL was an early language to be compiled on multiple architectures, in 1960. In many application domains the idea of using a higher level language quickly caught on, because of the expanding functionality supported by newer programming languages and the increasing complexity of computer architectures, compilers have become more complex. Early compilers were written in assembly language, the first self-hosting compiler – capable of compiling its own source code in a high-level language – was created in 1962 for the Lisp programming language by Tim Hart and Mike Levin at MIT. Since the 1970s, it has become practice to implement a compiler in the language it compiles
29.
Ada (programming language)
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Ada is a structured, statically typed, imperative, wide-spectrum, and object-oriented high-level computer programming language, extended from Pascal and other languages. It has built-in language support for design-by-contract, extremely strong typing, explicit concurrency, offering tasks, synchronous message passing, protected objects, Ada improves code safety and maintainability by using the compiler to find errors in favor of runtime errors. Ada is a standard, the current version is defined by ISO/IEC8652,2012. Ada was named after Ada Lovelace, who has credited with being the first computer programmer. Ada was originally targeted at embedded and real-time systems, the Ada 95 revision, designed by S. Tucker Taft of Intermetrics between 1992 and 1995, improved support for systems, numerical, financial, and object-oriented programming. Features of Ada include, strong typing, modularity mechanisms, run-time checking, parallel processing, exception handling, Ada 95 added support for object-oriented programming, including dynamic dispatch. The syntax of Ada minimizes choices of ways to perform basic operations, Ada uses the basic arithmetical operators +, -, *, and /, but avoids using other symbols. Code blocks are delimited by words such as declare, begin, and end, in the case of conditional blocks this avoids a dangling else that could pair with the wrong nested if-expression in other languages like C or Java. Ada is designed for development of large software systems. Ada packages can be compiled separately, Ada package specifications can also be compiled separately without the implementation to check for consistency. This makes it possible to detect problems early during the design phase, for example, the syntax requires explicitly named closing of blocks to prevent errors due to mismatched end tokens. The adherence to strong typing allows detection of common software errors either during compile-time. As concurrency is part of the specification, the compiler can in some cases detect potential deadlocks. Compilers also commonly check for misspelled identifiers, visibility of packages, redundant declarations, etc. and can provide warnings and useful suggestions on how to fix the error. Ada also supports run-time checks to protect against access to unallocated memory, buffer overflow errors, range violations, off-by-one errors, array access errors and these checks can be disabled in the interest of runtime efficiency, but can often be compiled efficiently. It also includes facilities to help program verification, for these reasons, Ada is widely used in critical systems, where any anomaly might lead to very serious consequences, e. g. accidental death, injury or severe financial loss. Examples of systems where Ada is used include avionics, ATC, railways, banking, military, adas dynamic memory management is high-level and type-safe. Ada does not have generic or untyped pointers, nor does it implicitly declare any pointer type, instead, all dynamic memory allocation and deallocation must take place through explicitly declared access types
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Python (programming language)
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Python is a widely used high-level programming language for general-purpose programming, created by Guido van Rossum and first released in 1991. The language provides constructs intended to enable writing clear programs on both a small and large scale and it has a large and comprehensive standard library. Python interpreters are available for operating systems, allowing Python code to run on a wide variety of systems. CPython, the implementation of Python, is open source software and has a community-based development model. CPython is managed by the non-profit Python Software Foundation, about the origin of Python, Van Rossum wrote in 1996, Over six years ago, in December 1989, I was looking for a hobby programming project that would keep me occupied during the week around Christmas. Would be closed, but I had a computer. I decided to write an interpreter for the new scripting language I had been thinking about lately, I chose Python as a working title for the project, being in a slightly irreverent mood. Python 2.0 was released on 16 October 2000 and had major new features, including a cycle-detecting garbage collector. With this release the development process was changed and became more transparent, Python 3.0, a major, backwards-incompatible release, was released on 3 December 2008 after a long period of testing. Many of its features have been backported to the backwards-compatible Python 2.6. x and 2.7. x version series. The End Of Life date for Python 2.7 was initially set at 2015, many other paradigms are supported via extensions, including design by contract and logic programming. Python uses dynamic typing and a mix of reference counting and a garbage collector for memory management. An important feature of Python is dynamic name resolution, which binds method, the design of Python offers some support for functional programming in the Lisp tradition. The language has map, reduce and filter functions, list comprehensions, dictionaries, and sets, the standard library has two modules that implement functional tools borrowed from Haskell and Standard ML. Python can also be embedded in existing applications that need a programmable interface, while offering choice in coding methodology, the Python philosophy rejects exuberant syntax, such as in Perl, in favor of a sparser, less-cluttered grammar. As Alex Martelli put it, To describe something as clever is not considered a compliment in the Python culture. Pythons philosophy rejects the Perl there is more one way to do it approach to language design in favor of there should be one—and preferably only one—obvious way to do it. Pythons developers strive to avoid premature optimization, and moreover, reject patches to non-critical parts of CPython that would offer an increase in speed at the cost of clarity
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Ruby (programming language)
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Ruby is a dynamic, reflective, object-oriented, general-purpose programming language. It was designed and developed in the mid-1990s by Yukihiro Matz Matsumoto in Japan, according to its creator, Ruby was influenced by Perl, Smalltalk, Eiffel, Ada, and Lisp. It supports multiple programming paradigms, including functional, object-oriented, and it also has a dynamic type system and automatic memory management. Ruby was conceived on February 24,1993, I knew Perl, but I didnt like it really, because it had the smell of a toy language. The object-oriented language seemed very promising, but I didnt like it, because I didnt think it was a true object-oriented language — OO features appeared to be add-on to the language. As a language maniac and OO fan for 15 years, I really wanted a genuine object-oriented, I looked for but couldnt find one. The name Ruby originated during a chat session between Matsumoto and Keiju Ishitsuka on February 24,1993, before any code had been written for the language. Initially two names were proposed, Coral and Ruby, Matsumoto chose the latter in a later e-mail to Ishitsuka. Matsumoto later noted a factor in choosing the name Ruby – it was the birthstone of one of his colleagues, the first public release of Ruby 0.95 was announced on Japanese domestic newsgroups on December 21,1995. Subsequently, three versions of Ruby were released in two days. The release coincided with the launch of the Japanese-language ruby-list mailing list, in the same year, Matsumoto was hired by netlab. jp to work on Ruby as a full-time developer. In 1998, the Ruby Application Archive was launched by Matsumoto, in 1999, the first English language mailing list ruby-talk began, which signaled a growing interest in the language outside Japan. In this same year, Matsumoto and Keiju Ishitsuka wrote the first book on Ruby, The Object-oriented Scripting Language Ruby and it would be followed in the early 2000s by around 20 books on Ruby published in Japanese. By 2000, Ruby was more popular than Python in Japan, in September 2000, the first English language book Programming Ruby was printed, which was later freely released to the public, further widening the adoption of Ruby amongst English speakers. In early 2002, the English-language ruby-talk mailing list was receiving more messages than the Japanese-language ruby-list, Ruby 1.8 was initially released in August 2003, was stable for a long time, and was retired June 2013. Although deprecated, there is still based on it. Ruby 1.8 is only compatible with Ruby 1.9. Ruby 1.8 has been the subject of industry standards
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Scala (programming language)
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Scala is a general-purpose programming language providing support for functional programming and a strong static type system. Designed to be concise, many of Scalas design decisions were designed to build from criticisms of Java, Scala source code is intended to be compiled to Java bytecode, so that the resulting executable code runs on a Java virtual machine. Scala provides language interoperability with Java, so that libraries written in languages may be referenced directly in Scala or Java code. Like Java, Scala is object-oriented, and uses a syntax reminiscent of the C programming language. Unlike Java, Scala has many features of programming languages like Scheme, Standard ML and Haskell, including currying, type inference, immutability, lazy evaluation. It also has a type system supporting algebraic data types, covariance and contravariance, higher-order types. Other features of Scala not present in Java include operator overloading, optional parameters, named parameters, raw strings, the name Scala is a portmanteau of scalable and language, signifying that it is designed to grow with the demands of its users. The design of Scala started in 2001 at the École Polytechnique Fédérale de Lausanne by Martin Odersky and it followed on from work on Funnel, a programming language combining ideas from functional programming and Petri nets. Odersky formerly worked on Generic Java, and javac, Suns Java compiler, after an internal release in late 2003, Scala was released publicly in early 2004 on the Java platform, A second version followed in March 2006. Although Scala had extensive support for programming from its inception. On 17 January 2011 the Scala team won a research grant of over €2.3 million from the European Research Council. On 12 May 2011, Odersky and collaborators launched Typesafe Inc. a company to provide support, training. Typesafe received a $3 million investment in 2011 from Greylock Partners, Scala runs on the Java platform and is compatible with existing Java programs. The reference Scala software distribution, including compiler and libraries, is released under a BSD license, Scala. js is a Scala compiler that compiles to JavaScript, making it possible to write Scala programs that can run in web browsers. Scala Native is a Scala compiler that targets the LLVM compiler infrastructure to create code that uses a lightweight managed runtime which utilizes the Boehm garbage collector. The project is led by Denys Shabalin and had its first release,0.1, a reference Scala compiler targeting the. NET Framework and its Common Language Runtime was released in June 2004, but was officially dropped in 2012. Indeed, Scalas compiling and executing model is identical to that of Java, a shorter version of the Hello World Scala program is, Scala includes interactive shell and scripting support. Saved in a file named HelloWorld2. scala, this can be run as a script with no prior compiling using, value types are capitalized, Int, Double, Boolean instead of int, double, boolean
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Clojure
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Clojure is a dialect of the Lisp programming language created by Rich Hickey. Clojure is a programming language with an emphasis on functional programming. It runs on the Java virtual machine and the Common Language Runtime, like other Lisps, Clojure treats code as data and has a macro system. The current development process is community-driven, overseen by Rich Hickey as its benevolent dictator for life, Clojure encourages immutability and immutable data structures. While its type system is dynamic, recent efforts have also sought the implementation of gradual typing. Clojure encourages programmers to be explicit about managing state and identity and this focus on programming with immutable values and explicit progression-of-time constructs is intended to facilitate developing more robust programs, especially multithreaded ones. Clojure is used in industry by such as Funding Circle, Walmart, Puppet Labs. Commercial support for Clojure is provided by Cognitect, annual Clojure conferences are organised every year across the globe, the most famous of them being Clojure/conj, Clojure/West, and EuroClojure. The latest stable version of Clojure is 1.8, released on January 19,2016, the first stable release was version 1.0, released on May 4,2009. Clojure is free software released under the Eclipse Public License, Rich Hickey is the creator of the Clojure language. Before Clojure, he developed dotLisp, a project based on the. Hickey spent about 2½ years working on Clojure before releasing it publicly, at the end of this time, Hickey sent an email announcing the language to some friends in the Common Lisp community. The development process is community-driven and is managed at the Clojure Community website, the website contains planning documents and an issue tracker where bugs may be filed. General development discussion occurs at the Clojure Dev Google Group, while anyone can submit bug reports and ideas, to contribute patches one must sign the Clojure Contributor agreement. JIRA tickets are processed by a team of screeners and finally Rich Hickey approves the changes, Rich Hickey developed Clojure because he wanted a modern Lisp for functional programming, symbiotic with the established Java platform, and designed for concurrency. Clojures approach to state is characterized by the concept of identities, since states are immutable values, any number of workers can operate on them in parallel, and concurrency becomes a question of managing changes from one state to another. For this purpose, Clojure provides several mutable reference types, each having well-defined semantics for the transition between states. Clojure runs on the Java virtual machine and as a result integrates with Java and fully supports calling Java code from Clojure, the community uses Leiningen for project automation, providing support for Maven integration
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Groovy (programming language)
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Apache Groovy is an object-oriented programming language for the Java platform. It is a language with features similar to those of Python, Ruby, Perl. It can be used as a language for the Java Platform, is dynamically compiled to Java virtual machine bytecode. Groovy uses a Java-like curly-bracket syntax, most Java code is also syntactically valid Groovy, although semantics may be different. Groovy 1.0 was released on January 2,2007, since version 2, Groovy can also be compiled statically, offering type inference, and performance near that of Java. Groovy 2.4 was the last major release under Pivotal Softwares sponsorship which ended in March 2015, Groovy has since changed its governance structure to a Project Management Committee in the Apache Software Foundation. James Strachan first talked about the development of Groovy on his blog in August 2003, several versions were released between 2004 and 2006. After the Java Community Process standardization effort began, the version numbering changed and a version called 1.0 was released on January 2,2007. After various betas and release candidates numbered 1.1, on December 7,2007, Groovy 1.1 Final was released, in 2007, Groovy won the first prize at JAX2007 innovation award. In 2008, Grails, a Groovy web framework, won the prize at JAX2008 innovation award. In November 2008, SpringSource acquired the Groovy and Grails company, in August 2009 VMWare acquired SpringSource. Strachan had left the project silently a year before the Groovy 1.0 release in 2007, in Oct 2016, Strachan stated I still love groovy, java, go, typescript and kotlin. In March 2004, Groovy had been submitted to the JCP as JSR241, after 8 years of inactivity, the Spec Lead changed its status to dormant in April 2012. On July 2,2012, Groovy 2.0 was released, when the Pivotal Software joint venture was spun-off by EMC Corporation and VMware in April 2013, Groovy and Grails formed part of its product portfolio. Pivotal ceased sponsoring Groovy and Grails from April 2015 and that same month, Groovy changed its governance structure from a Codehaus repository to a Project Management Committee in the Apache Software Foundation via its incubator. Groovy graduated from Apaches incubator and became a project in November 2015. Most valid Java files are also valid Groovy files, although the two languages are similar, Groovy code can be more compact, because it does not need all the elements that Java needs. This makes it possible for Java programmers to learn Groovy gradually by starting with familiar Java syntax before acquiring more Groovy programming idioms. to check automatically for null pointers
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Java syntax
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The syntax of the Java programming language is the set of rules defining how a Java program is written and interpreted. The syntax is derived from C and C++. Unlike C++, in Java there are no global functions or variables, all code belongs to classes and all values are objects. The only exception is the types, which are not represented by a class instance for performance reasons. Some features like operator overloading or unsigned integer types are omitted to simplify the language, the Java syntax has been gradually extended in the course of the eight major JDK releases support capabilities such as generic programming and function literals. An identifier is the name of an element in the code, there are certain standard naming conventions to follow when selecting names for elements. An identifier can contain, Any Unicode character that is a letter or digit, an identifier cannot, Start with a digit. Be equal to a keyword, null literal or boolean literal. Integer literals are of int type by default unless long type is specified by appending L or l suffix to the literal, e. g. 367L. Since Java SE7, it is possible to include underscores between the digits of a number to increase readability, for example, a number 145608987 can be written as 145_608_987, variables are identifiers associated with values. They are declared by writing the variables type and name, and are initialized in the same statement by assigning a value. Multiple variables of the type can be declared and initialized in one statement using comma as a delimiter. The separators signify a code block and a new scope, Class members and the body of a method are examples of what can live inside these braces in various contexts. Inside of method bodies, you can use braces to create new scopes, as follows, traditional comments, also known as block comments, start with /* and end with */, they may span across multiple lines. This type of comment was derived from C and C++, end-of-line comments start with // and extend to the end of the current line. This comment type is present in C++ and in modern C. Documentation comments in the files are processed by the Javadoc tool to generate documentation. This type of comment is identical to traditional comments, except it starts with /**, technically, these comments are a special kind of traditional comment and they are not specifically defined in the language specification
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C (programming language)
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C was originally developed by Dennis Ritchie between 1969 and 1973 at Bell Labs, and used to re-implement the Unix operating system. C has been standardized by the American National Standards Institute since 1989, C is an imperative procedural language. Therefore, C was useful for applications that had formerly been coded in assembly language. Despite its low-level capabilities, the language was designed to encourage cross-platform programming, a standards-compliant and portably written C program can be compiled for a very wide variety of computer platforms and operating systems with few changes to its source code. The language has become available on a wide range of platforms. In C, all code is contained within subroutines, which are called functions. Function parameters are passed by value. Pass-by-reference is simulated in C by explicitly passing pointer values, C program source text is free-format, using the semicolon as a statement terminator and curly braces for grouping blocks of statements. The C language also exhibits the characteristics, There is a small, fixed number of keywords, including a full set of flow of control primitives, for, if/else, while, switch. User-defined names are not distinguished from keywords by any kind of sigil, There are a large number of arithmetical and logical operators, such as +, +=, ++, &, ~, etc. More than one assignment may be performed in a single statement, function return values can be ignored when not needed. Typing is static, but weakly enforced, all data has a type, C has no define keyword, instead, a statement beginning with the name of a type is taken as a declaration. There is no function keyword, instead, a function is indicated by the parentheses of an argument list, user-defined and compound types are possible. Heterogeneous aggregate data types allow related data elements to be accessed and assigned as a unit, array indexing is a secondary notation, defined in terms of pointer arithmetic. Unlike structs, arrays are not first-class objects, they cannot be assigned or compared using single built-in operators, There is no array keyword, in use or definition, instead, square brackets indicate arrays syntactically, for example month. Enumerated types are possible with the enum keyword and they are not tagged, and are freely interconvertible with integers. Strings are not a data type, but are conventionally implemented as null-terminated arrays of characters. Low-level access to memory is possible by converting machine addresses to typed pointers
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Smalltalk
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Smalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the new world of computing exemplified by human–computer symbiosis, the language was first generally released as Smalltalk-80. Smalltalk-like languages are in continuing development and have gathered loyal communities of users around them. ANSI Smalltalk was ratified in 1998 and represents the version of Smalltalk. There are a number of Smalltalk variants. The unqualified word Smalltalk is often used to indicate the Smalltalk-80 language, Smalltalk was the product of research led by Alan Kay at Xerox Palo Alto Research Center, Alan Kay designed most of the early Smalltalk versions, which Dan Ingalls implemented. A later variant actually used for work is now known as Smalltalk-72. Its syntax and execution model were very different from modern Smalltalk variants, after significant revisions which froze some aspects of execution semantics to gain performance, Smalltalk-76 was created. This system had a development environment featuring most of the now familiar tools, later a general availability implementation, known as Smalltalk-80 Version 2, was released as an image and a virtual machine specification. ANSI Smalltalk has been the standard language reference since 1998, two of the currently popular Smalltalk implementation variants are descendants of those original Smalltalk-80 images. Squeak is an open source implementation derived from Smalltalk-80 Version 1 by way of Apple Smalltalk, VisualWorks is derived from Smalltalk-80 version 2 by way of Smalltalk-802.5 and ObjectWorks. As an interesting link between generations, in 2001 Vassili Bykov implemented Hobbes, a machine running Smalltalk-80 inside VisualWorks. During the late 1980s to mid-1990s, Smalltalk environments—including support, training, ParcPlace Systems tended to focus on the Unix/Sun microsystems market, while Digitalk focused on Intel-based PCs running Microsoft Windows or IBMs OS/2. IBM initially supported the Digitalk product, but then entered the market with a Smalltalk product in 1995 called VisualAge/Smalltalk, easel introduced Enfin at this time on Windows and OS/2. Enfin became far more popular in Europe, as IBM introduced it into IT shops before their development of IBM Smalltalk, Enfin was later acquired by Cincom Systems, and is now sold under the name ObjectStudio, and is part of the Cincom Smalltalk product suite. In 1995, ParcPlace and Digitalk merged into ParcPlace-Digitalk and then rebranded in 1997 as ObjectShare, located in Irvine, ObjectShare was traded publicly until 1999, when it was delisted and dissolved. The merged firm never managed to find a response to Java as to market positioning. VisualWorks was sold to Cincom and is now part of Cincom Smalltalk, Cincom has backed Smalltalk strongly, releasing multiple new versions of VisualWorks and ObjectStudio each year since 1999
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Pointer (computer programming)
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In computer science, a pointer is a programming language object, whose value refers to another value stored elsewhere in the computer memory using its memory address. A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer. As an analogy, a number in a books index could be considered a pointer to the corresponding page. Pointers to data significantly improve performance for operations such as traversing strings, lookup tables, control tables. In particular, it is much cheaper in time and space to copy and dereference pointers than it is to copy. Pointers are also used to hold the addresses of entry points for called subroutines in procedural programming, in object-oriented programming, pointers to functions are used for binding methods, often using what are called virtual method tables. A pointer is a simple, more concrete implementation of the more abstract data type. Several languages support some type of pointer, although some have more restrictions on their use than others, because pointers allow both protected and unprotected access to memory addresses, there are risks associated with using them particularly in the latter case. Other measures may also be taken, harold Lawson is credited with the 1964 invention of the pointer. According to the Oxford English Dictionary, the word pointer first appeared in print as a pointer in a technical memorandum by the System Development Corporation. In computer science, a pointer is a kind of reference, a data primitive is any datum that can be read from or written to computer memory using one memory access. A data aggregate is a group of primitives that are contiguous in memory. In the context of these definitions, a byte is the smallest primitive, the memory address of the initial byte of a datum is considered the memory address of the entire datum. A memory pointer is a primitive, the value of which is intended to be used as a memory address and it is also said that a pointer points to a datum when the pointers value is the datums memory address. More generally, a pointer is a kind of reference, and it is said that a pointer references a datum stored somewhere in memory, to obtain that datum is to dereference the pointer. The feature that separates pointers from other kinds of reference is that a value is meant to be interpreted as a memory address. References serve as a level of indirection, A pointers value determines which memory address is to be used in a calculation, when setting up data structures like lists, queues and trees, it is necessary to have pointers to help manage how the structure is implemented and controlled. Typical examples of pointers are start pointers, end pointers, and these pointers can either be absolute or relative
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Memory management
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Memory management is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request and this is critical to any advanced computer system where more than a single process might be underway at any time. Several methods have been devised that increase the effectiveness of memory management, the quality of the virtual memory manager can have an extensive effect on overall system performance. Modern general-purpose computer systems manage memory at two levels, operating system level, and application level, application-level memory management is generally categorized as either automatic memory management, usually involving garbage collection, or manual memory management. The task of fulfilling an allocation request consists of locating a block of unused memory of sufficient size, Memory requests are satisfied by allocating portions from a large pool of memory called the heap or free store. At any given time, some parts of the heap are in use, while some are free, the allocators metadata can also inflate the size of small allocations. This is often managed by chunking, the memory management system must track outstanding allocations to ensure that they do not overlap and that no memory is ever lost as a memory leak. The specific dynamic memory allocation algorithm implemented can impact performance significantly, a study conducted in 1994 by Digital Equipment Corporation illustrates the overheads involved for a variety of allocators. The lowest average instruction path length required to allocate a single memory slot was 52, since the precise location of the allocation is not known in advance, the memory is accessed indirectly, usually through a pointer reference. This works well for simple embedded systems where no large objects need to be allocated, however, due to the significantly reduced overhead this method can substantially improve performance for objects that need frequent allocation / de-allocation and is often used in video games. All blocks of a particular size are kept in a linked list or tree. If a smaller size is requested than is available, the smallest available size is selected, one of the resulting parts is selected, and the process repeats until the request is complete. When a block is allocated, the allocator will start with the smallest sufficiently large block to avoid needlessly breaking blocks, when a block is freed, it is compared to its buddy. If they are free, they are combined and placed in the correspondingly larger-sized buddy-block list. Virtual memory is a method of decoupling the memory organization from the physical hardware, the applications operate memory via virtual addresses. Each time an attempt to access stored data is made, virtual memory data orders translate the virtual address to a physical address, in this way addition of virtual memory enables granular control over memory systems and methods of access. In virtual memory systems the system limits how a process can access the memory. Even though the memory allocated for specific processes is normally isolated, shared memory is one of the fastest techniques for inter-process communication
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