In computing , a shell is a computer program that exposes an operating system 's services to a human user or other programs. In general, operating system shells use either a command-line interface (CLI) or graphical user interface (GUI), depending on a computer's role and particular operation. It is named a shell because it is the outermost layer around the operating system.
72-478: GNOME Shell is the graphical shell of the GNOME desktop environment starting with version 3 , which was released on April 6, 2011. It provides basic functions like launching applications and switching between windows , and is also a widget engine . GNOME Shell replaced GNOME Panel and some ancillary components of GNOME 2. GNOME Shell is written in C and JavaScript as a plugin for Mutter . In contrast to
144-522: A read–eval–print loop, REPL ). Since the operating system shell is actually an application, it may easily be replaced with another similar application, for most operating systems. In addition to shells running on local systems, there are different ways to make remote systems available to local users; such approaches are usually referred to as remote access or remote administration. Initially available on multi-user mainframes , which provided text-based UIs for each active user simultaneously by means of
216-544: A procedural language such as Lua could consist primarily of basic routines to execute code, manipulate data or handle errors while an API for an object-oriented language , such as Java, would provide a specification of classes and its class methods . Hyrum's law states that "With a sufficient number of users of an API, it does not matter what you promise in the contract: all observable behaviors of your system will be depended on by somebody." Meanwhile, several studies show that most applications that use an API tend to use
288-420: A software framework : a framework can be based on several libraries implementing several APIs, but unlike the normal use of an API, the access to the behavior built into the framework is mediated by extending its content with new classes plugged into the framework itself. Moreover, the overall program flow of control can be out of the control of the caller and in the framework's hands by inversion of control or
360-432: A teletypewriter can send codes representing keystrokes to a command interpreter program running on the computer; the command interpreter parses the sequence of keystrokes and responds with an error message if it cannot recognize the sequence of characters, or it may carry out some other program action such as loading an application program, listing files, logging in a user and many others. Operating systems such as UNIX have
432-688: A text terminal connected to the mainframe via serial line or modem , remote access has extended to Unix-like systems and Microsoft Windows. On Unix-like systems, Secure Shell protocol (SSH) is usually used for text-based shells, while SSH tunneling can be used for X Window System –based graphical user interfaces (GUIs). On Microsoft Windows, Remote Desktop Protocol can be used to provide GUI remote access, and since Windows Vista , PowerShell Remote can be used for text-based remote access via WMI, RPC, and WS-Management. Most operating system shells fall into one of two categories – command-line and graphical. Command-line shells provide
504-496: A user interface , an API is typically not visible to users. It is an "under the hood" portion of a software system, used for machine-to-machine communication. A well-designed API exposes only objects or actions needed by software or software developers. It hides details that have no use. This abstraction simplifies programming. Building software using APIs has been compared to using building-block toys, such as Lego bricks. Software services or software libraries are analogous to
576-684: A Mutter plugin largely written in JavaScript and uses GUI widgets provided by GTK+ version 3. Changes to the user interface (UI) include, but are not limited to: The functionality of GNOME Shell can be changed with extensions , which can be written in JavaScript . Users can find and install extensions using the GNOME extensions website. Some of these extensions are hosted in GNOME's git repository , though they are not official. GNOME Shell has received mixed reviews: it has been criticized for
648-449: A broad term describing much of the communication on the internet. When used in this way, the term API has overlap in meaning with the term communication protocol . The interface to a software library is one type of API. The API describes and prescribes the "expected behavior" (a specification) while the library is an "actual implementation" of this set of rules. A single API can have multiple implementations (or none, being abstract) in
720-517: A business ecosystem. The main policies for releasing an API are: An important factor when an API becomes public is its "interface stability". Changes to the API—for example adding new parameters to a function call—could break compatibility with the clients that depend on that API. When parts of a publicly presented API are subject to change and thus not stable, such parts of a particular API should be documented explicitly as "unstable". For example, in
792-460: A client would need to know for practical purposes. Documentation is crucial for the development and maintenance of applications using the API. API documentation is traditionally found in documentation files but can also be found in social media such as blogs, forums, and Q&A websites. Traditional documentation files are often presented via a documentation system, such as Javadoc or Pydoc, that has
SECTION 10
#1732775919398864-424: A command-line interface (CLI) to the operating system, while graphical shells provide a graphical user interface (GUI). Other possibilities, although not so common, include a voice user interface and various implementations of a text-based user interface (TUI) that are not CLI, such as text-based menu systems. The relative merits of CLI- and GUI-based shells are often debated. Many computer users use both depending on
936-459: A command-line interface. For example, in Unix-like systems, the telnet program has a number of commands for controlling a link to a remote computer system. Since the commands to the program are made of the same keystrokes as the data being sent to a remote computer, some means of distinguishing the two are required. An escape sequence can be defined, using either a special local keystroke that
1008-433: A connection or interface is called an API specification . A computer system that meets this standard is said to implement or expose an API. The term API may refer either to the specification or to the implementation. In contrast to a user interface , which connects a computer to a person, an application programming interface connects computers or pieces of software to each other. It is not intended to be used directly by
1080-435: A consistent appearance and structure. However, the types of content included in the documentation differs from API to API. In the interest of clarity, API documentation may include a description of classes and methods in the API as well as "typical usage scenarios, code snippets, design rationales, performance discussions, and contracts", but implementation details of the API services themselves are usually omitted. It can take
1152-534: A given API, it is possible to infer the typical usages, as well the required contracts and directives. Then, templates can be used to generate natural language from the mined data. In 2010, Oracle Corporation sued Google for having distributed a new implementation of Java embedded in the Android operating system. Google had not acquired any permission to reproduce the Java API, although permission had been given to
1224-530: A large variety of shell programs with different commands, syntax and capabilities, with the POSIX shell being a baseline. Some operating systems had only a single style of command interface; commodity operating systems such as MS-DOS came with a standard command interface ( COMMAND.COM ) but third-party interfaces were also often available, providing additional features or functions such as menuing or remote program execution. Application programs may also implement
1296-441: A modular software library in the 1940s for EDSAC , an early computer. The subroutines in this library were stored on punched paper tape organized in a filing cabinet . This cabinet also contained what Wilkes and Wheeler called a "library catalog" of notes about each subroutine and how to incorporate it into a program. Today, such a catalog would be called an API (or an API specification or API documentation) because it instructs
1368-470: A number of forms, including instructional documents, tutorials, and reference works. It'll also include a variety of information types, including guides and functionalities. Restrictions and limitations on how the API can be used are also covered by the documentation. For instance, documentation for an API function could note that its parameters cannot be null, that the function itself is not thread safe . Because API documentation tends to be comprehensive, it
1440-529: A person (the end user ) other than a computer programmer who is incorporating it into software. An API is often made up of different parts which act as tools or services that are available to the programmer. A program or a programmer that uses one of these parts is said to call that portion of the API. The calls that make up the API are also known as subroutines , methods, requests, or endpoints . An API specification defines these calls, meaning that it explains how to use or implement them. One purpose of APIs
1512-440: A programmer on how to use (or "call") each subroutine that the programmer needs. Wilkes and Wheeler's book The Preparation of Programs for an Electronic Digital Computer contains the first published API specification. Joshua Bloch considers that Wilkes and Wheeler "latently invented" the API, because it is more of a concept that is discovered than invented. The term "application program interface" (without an -ing suffix)
SECTION 20
#17327759193981584-433: A purpose-built program. Several command-line shells, such as Nushell , Xonsh, Bash (Unix shell) , and Z shell , offer command-line completion , enabling the interpreter to expand commands based on a few characters input by the user. A command-line interpreter may offer a history function, so that the user can recall earlier commands issued to the system and repeat them, possibly with some editing. Since all commands to
1656-419: A set of loosely coupled utilities. Most graphical user interfaces develop the metaphor of an "electronic desktop" , where data files are represented as if they were paper documents on a desk, and application programs similarly have graphical representations instead of being invoked by command names. Graphical shells typically build on top of a windowing system . In the case of X Window System or Wayland ,
1728-403: A shell is a piece of software that is an "empty" expert system without the knowledge base for any particular application. API An application programming interface ( API ) is a connection between computers or between computer programs . It is a type of software interface , offering a service to other pieces of software . A document or standard that describes how to build such
1800-643: A shipping company API that can be added to an eCommerce-focused website to facilitate ordering shipping services and automatically include current shipping rates, without the site developer having to enter the shipper's rate table into a web database. While "web API" historically has been virtually synonymous with web service , the recent trend (so-called Web 2.0 ) has been moving away from Simple Object Access Protocol ( SOAP ) based web services and service-oriented architecture (SOA) towards more direct representational state transfer (REST) style web resources and resource-oriented architecture (ROA). Part of this trend
1872-404: A similar mechanism. An API can specify the interface between an application and the operating system . POSIX , for example, specifies a set of common APIs that aim to enable an application written for a POSIX conformant operating system to be compiled for another POSIX conformant operating system. Linux and Berkeley Software Distribution are examples of operating systems that implement
1944-441: A small part of the API. Language bindings are also APIs. By mapping the features and capabilities of one language to an interface implemented in another language, a language binding allows a library or service written in one language to be used when developing in another language. Tools such as SWIG and F2PY, a Fortran -to- Python interface generator, facilitate the creation of such interfaces. An API can also be related to
2016-453: A variety of reasons, mostly related to design decisions and reduced user control over the environment. For example, users in the free software community have raised concerns that the planned tight integration with Mutter will mean that users of GNOME Shell will not be able to switch to an alternative window manager without breaking their desktop. In particular, users might not be able to use Compiz with GNOME Shell while retaining access to
2088-454: Is a challenge for writers to keep the documentation updated and for users to read it carefully, potentially yielding bugs. API documentation can be enriched with metadata information like Java annotations . This metadata can be used by the compiler, tools, and by the run-time environment to implement custom behaviors or custom handling. It is possible to generate API documentation in a data-driven manner. By observing many programs that use
2160-487: Is a good example of the former sort of application. LiteStep and Emerge Desktop are good examples of the latter. Interoperability programmes and purpose-designed software lets Windows users use equivalents of many of the various Unix-based GUIs discussed below, as well as Macintosh. An equivalent of the OS/2 Presentation Manager for version 3.0 can run some OS/2 programmes under some conditions using
2232-430: Is an API response . A weather forecasting app might integrate with a number of weather sensor APIs, gathering weather data from throughout a geographical area. An API is often compared to a contract . It represents an agreement between parties: a service provider who offers the API and the software developers who rely upon it. If the API remains stable, or if it changes only in predictable ways, developers' confidence in
GNOME Shell - Misplaced Pages Continue
2304-512: Is an architectural approach that revolves around providing a program interface to a set of services to different applications serving different types of consumers. When used in the context of web development , an API is typically defined as a set of specifications, such as Hypertext Transfer Protocol (HTTP) request messages, along with a definition of the structure of response messages, usually in an Extensible Markup Language ( XML ) or JavaScript Object Notation ( JSON ) format. An example might be
2376-522: Is created in one place dynamically can be posted and updated to multiple locations on the web. For example, Twitter's REST API allows developers to access core Twitter data and the Search API provides methods for developers to interact with Twitter Search and trends data. The design of an API has significant impact on its usage. The principle of information hiding describes the role of programming interfaces as enabling modular programming by hiding
2448-399: Is first recorded in a paper called Data structures and techniques for remote computer graphics presented at an AFIPS conference in 1968. The authors of this paper use the term to describe the interaction of an application—a graphics program in this case—with the rest of the computer system. A consistent application interface (consisting of Fortran subroutine calls) was intended to free
2520-471: Is never passed on but always interpreted by the local system. The program becomes modal, switching between interpreting commands from the keyboard or passing keystrokes on as data to be processed. A feature of many command-line shells is the ability to save sequences of commands for re-use. A data file can contain sequences of commands which the CLI can be made to follow as if typed in by a user. Special features in
2592-453: Is now the most common meaning of the term API. The Semantic Web proposed by Tim Berners-Lee in 2001 included "semantic APIs" that recast the API as an open , distributed data interface rather than a software behavior interface. Proprietary interfaces and agents became more widespread than open ones, but the idea of the API as a data interface took hold. Because web APIs are widely used to exchange data of all kinds online, API has become
2664-475: Is related to the Semantic Web movement toward Resource Description Framework (RDF), a concept to promote web-based ontology engineering technologies. Web APIs allow the combination of multiple APIs into new applications known as mashups . In the social media space, web APIs have allowed web communities to facilitate sharing content and data between communities and applications. In this way, content that
2736-440: Is to hide the internal details of how a system works, exposing only those parts a programmer will find useful and keeping them consistent even if the internal details later change. An API may be custom-built for a particular pair of systems, or it may be a shared standard allowing interoperability among many systems. The term API is often used to refer to web APIs , which allow communication between computers that are joined by
2808-549: The Google Guava library, the parts that are considered unstable, and that might change soon, are marked with the Java annotation @Beta . A public API can sometimes declare parts of itself as deprecated or rescinded. This usually means that part of the API should be considered a candidate for being removed, or modified in a backward incompatible way. Therefore, these changes allow developers to transition away from parts of
2880-686: The Java language in particular. In the 1990s, with the spread of the internet , standards like CORBA , COM , and DCOM competed to become the most common way to expose API services. Roy Fielding 's dissertation Architectural Styles and the Design of Network-based Software Architectures at UC Irvine in 2000 outlined Representational state transfer (REST) and described the idea of a "network-based Application Programming Interface" that Fielding contrasted with traditional "library-based" APIs. XML and JSON web APIs saw widespread commercial adoption beginning in 2000 and continuing as of 2021. The web API
2952-512: The Java remote method invocation API uses the Java Remote Method Protocol to allow invocation of functions that operate remotely, but appear local to the developer. Therefore, remote APIs are useful in maintaining the object abstraction in object-oriented programming ; a method call , executed locally on a proxy object, invokes the corresponding method on the remote object, using the remoting protocol, and acquires
GNOME Shell - Misplaced Pages Continue
3024-682: The KDE Plasma Workspaces , a software framework intended to facilitate the creation of multiple graphical shells for different devices, the GNOME Shell is intended to be used on desktop computers with large screens operated via keyboard and mouse , as well as portable computers with smaller screens operated via their keyboard , touchpad or touchscreen . The first concepts for GNOME Shell were created during GNOME's User Experience Hackfest 2008 in Boston. After criticism of
3096-556: The Linux Standard Base provides an ABI. Remote APIs allow developers to manipulate remote resources through protocols , specific standards for communication that allow different technologies to work together, regardless of language or platform. For example, the Java Database Connectivity API allows developers to query many different types of databases with the same set of functions, while
3168-911: The Thompson shell in the first version of Unix. While simpler than the Multics shell, it contained some innovative features, which have been carried forward in modern shells, including the use of < and > for input and output redirection . The graphical shell first appeared in Douglas Engelbart ’s NLS system, demonstrated in December, 1968 at the Fall Joint Computer Conference in San Francisco, in what has been called The Mother of All Demos . Engelbart’s colleagues at Stanford Research Institute brought
3240-479: The internet . There are also APIs for programming languages , software libraries , computer operating systems , and computer hardware . APIs originated in the 1940s, though the term did not emerge until the 1960s and 70s. An API opens a software system to interactions from the outside. It allows two software systems to communicate across a boundary — an interface — using mutually agreed-upon signals. In other words, an API connects software entities together. Unlike
3312-443: The 95 and NT types at least through Windows XP. The interfaces of Windows versions 1 and 2 were markedly different. Desktop applications are also considered shells, as long as they use a third-party engine. Likewise, many individuals and developers dissatisfied with the interface of Windows Explorer have developed software that either alters the functioning and appearance of the shell or replaces it entirely. WindowBlinds by StarDock
3384-461: The API that will be removed or not supported in the future. Client code may contain innovative or opportunistic usages that were not intended by the API designers. In other words, for a library with a significant user base, when an element becomes part of the public API, it may be used in diverse ways. On February 19, 2020, Akamai published their annual “State of the Internet” report, showcasing
3456-489: The API will increase. This may increase their use of the API. The term API initially described an interface only for end-user-facing programs, known as application programs . This origin is still reflected in the name "application programming interface." Today, the term is broader, including also utility software and even hardware interfaces . The idea of the API is much older than the term itself. British computer scientists Maurice Wilkes and David Wheeler worked on
3528-580: The CLI may apply when it is carrying out these stored instructions. Such batch files (script files) can be used repeatedly to automate routine operations such as initializing a set of programs when a system is restarted. Batch mode use of shells usually involves structures, conditionals, variables, and other elements of programming languages; some have the bare essentials needed for such a purpose, others are very sophisticated programming languages in and of themselves. Conversely, some programming languages can be used interactively from an operating system shell or in
3600-482: The GNOME desktop environment, its design is guided by the GNOME UX Design Team. The GNOME Shell comprises the following graphical and functional elements: GNOME Shell is tightly integrated with Mutter , a compositing window manager and Wayland compositor . It is based upon Clutter to provide visual effects and hardware acceleration . According to GNOME Shell maintainer Owen Taylor, it is set up as
3672-558: The Microsoft Windows operating system use the Windows shell as their shell. Windows Shell provides desktop environment , start menu , and task bar , as well as a graphical user interface for accessing the file management functions of the operating system. Older versions also include Program Manager , which was the shell for the 3.x series of Microsoft Windows, and which in fact shipped with later versions of Windows of both
SECTION 50
#17327759193983744-459: The OS/2 environmental subsystem in versions of Windows NT. "Shell" is also used loosely to describe application software that is "built around" a particular component, such as web browsers and email clients, in analogy to the shells found in nature. Indeed, the (command-line) shell encapsulates the operating system kernel . These are also sometimes referred to as "wrappers". In expert systems ,
3816-502: The POSIX APIs. Microsoft has shown a strong commitment to a backward-compatible API, particularly within its Windows API (Win32) library, so older applications may run on newer versions of Windows using an executable-specific setting called "Compatibility Mode". An API differs from an application binary interface (ABI) in that an API is source code based while an ABI is binary based. For instance, POSIX provides APIs while
3888-401: The application programming interface separately from other interfaces, such as the query interface. Database professionals in the 1970s observed these different interfaces could be combined; a sufficiently rich application interface could support the other interfaces as well. This observation led to APIs that supported all types of programming, not just application programming. By 1990, the API
3960-413: The bricks; they may be joined together via their APIs, composing a new software product. The process of joining is called integration . As an example, consider a weather sensor that offers an API. When a certain message is transmitted to the sensor, it will detect the current weather conditions and reply with a weather report. The message that activates the sensor is an API call , and the weather report
4032-636: The concept to the Xerox Palo Alto Research Center (PARC), where it appeared on the Alto , introduced in 1973. From there the idea spread to Niklaus Wirth ’s Lilith in 1980, and the Apple Lisa in 1983, then became ubiquitous. A command-line interface (CLI) is an operating system shell that uses alphanumeric characters typed on a keyboard to provide instructions and data to the operating system, interactively. For example,
4104-420: The form of different libraries that share the same programming interface. The separation of the API from its implementation can allow programs written in one language to use a library written in another. For example, because Scala and Java compile to compatible bytecode , Scala developers can take advantage of any Java API. API use can vary depending on the type of programming language involved. An API for
4176-476: The growing trend of cybercriminals targeting public API platforms at financial services worldwide. From December 2017 through November 2019, Akamai witnessed 85.42 billion credential violation attacks. About 20%, or 16.55 billion, were against hostnames defined as API endpoints. Of these, 473.5 million have targeted financial services sector organizations. API documentation describes what services an API offers and how to use those services, aiming to cover everything
4248-429: The idea of "using commands somehow like a programming language," and coined the term shell to describe it. In a 1965 document, the shell is defined as "a common procedure called automatically by the supervisor whenever a user types in some message at his console, at a time when he has no other process in active execution under console control. This procedure acts as an interface between console messages and subroutine [in
4320-490: The implementation details of the modules so that users of modules need not understand the complexities inside the modules. Thus, the design of an API attempts to provide only the tools a user would expect. The design of programming interfaces represents an important part of software architecture , the organization of a complex piece of software. APIs are one of the more common ways technology companies integrate. Those that provide and use APIs are considered as being members of
4392-598: The operating system had to be typed by the user, short command names and compact systems for representing program options were common. Short names were sometimes hard for a user to recall, and early systems lacked the storage resources to provide a detailed on-line user instruction guide. A graphical user interface (GUI) provides means for manipulating programs graphically, by allowing for operations such as opening, closing, moving and resizing windows , as well as switching focus between windows. Graphical shells may be included with desktop environments or come separately, even as
SECTION 60
#17327759193984464-614: The programmer from dealing with idiosyncrasies of the graphics display device, and to provide hardware independence if the computer or the display were replaced. The term was introduced to the field of databases by C. J. Date in a 1974 paper called The Relational and Network Approaches: Comparison of the Application Programming Interface . An API became a part of the ANSI/SPARC framework for database management systems . This framework treated
4536-442: The result to be used locally as a return value. A modification of the proxy object will also result in a corresponding modification of the remote object. Web APIs are the defined interfaces through which interactions happen between an enterprise and applications that use its assets, which also is a Service Level Agreement (SLA) to specify the functional provider and expose the service path or URL for its API users. An API approach
4608-509: The same types of features that older versions of GNOME allowed. Reviews have generally become more positive over time, with upcoming releases addressing many of the annoyances reported by users. Graphical shell Operating systems provide various services to their users, including file management , process management (running and terminating applications ), batch processing , and operating system monitoring and configuration. Most operating system shells are not direct interfaces to
4680-561: The shell consists of an X window manager or a Wayland compositor , respectively, as well as of one or multiple programs providing the functionality to start installed applications, to manage open windows and virtual desktops, and often to support a widget engine. In the case of macOS , Quartz Compositor acts as the windowing system, and the shell consists of the Finder , the Dock , SystemUIServer, and Mission Control . Modern versions of
4752-452: The similar OpenJDK project. Judge William Alsup ruled in the Oracle v. Google case that APIs cannot be copyrighted in the U.S. and that a victory for Oracle would have widely expanded copyright protection to a "functional set of symbols" and allowed the copyrighting of simple software commands: To accept Oracle's claim would be to allow anyone to copyright one version of code to carry out
4824-451: The supervisor]." This system was first implemented by Glenda Schroeder and an unnamed man from General Electric . Multics also introduced the active function , a key concept in all later shells. This is defined as a string... which is replaced by a character string return value before the command line containing it is executed. Active functions are often used... to implement command-language macros. In 1971, Ken Thompson developed
4896-566: The system or a user process. The purpose of such a procedure is to create a medium of exchange into which one could activate any procedure, as if it were called from the inside of another program . Hereafter, for simplification, we shall refer to that procedure as the "SHELL". Louis Pouzin, The SHELL: A Global Tool for Calling and Chaining Procedures in the System In 1964, for the Multics operating system, Louis Pouzin conceived
4968-499: The task to be performed. Early interactive systems provided a simple command-line interpreter as part of the resident monitor . This interpreter might be called by different names, such as COMCON on DEC TOPS-10 systems. The interpreter would execute one of a number of predefined commands, one of which would be to run a user program. Common commands would log the user on and off the system, allocate, free, and manipulate devices and files, and query various pieces of information about
5040-697: The traditional GNOME desktop and accusations of stagnation and lacking vision, the resulting discussion led to the announcement of GNOME 3.0 in April 2009. Since then Red Hat has been the main driver of GNOME Shell's development. Pre-release versions of GNOME Shell were first made available in August 2009 and became regular, non-default part of GNOME in version 2.28 in September 2009. It was finally shipped as GNOME's default user interface on April 6, 2011. As graphical shell (graphical front-end/graphical shell/UX/UI) of
5112-440: The underlying kernel , even if a shell communicates with the user via peripheral devices attached to the computer directly. Shells are actually special applications that use the kernel API in just the same way as it is used by other application programs. A shell manages the user–system interaction by prompting users for input, interpreting their input, and then handling output from the underlying operating system (much like
5184-455: Was defined simply as "a set of services available to a programmer for performing certain tasks" by technologist Carl Malamud . The idea of the API was expanded again with the dawn of remote procedure calls and web APIs . As computer networks became common in the 1970s and 80s, programmers wanted to call libraries located not only on their local computers, but on computers located elsewhere. These remote procedure calls were well supported by
#397602