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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 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.

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82-563: The Windows API , informally WinAPI , is the foundational application programming interface (API) that allows a computer program to access the features of the Microsoft Windows operating system in which the program is running. Programs access API functionality via dynamic-link library (DLL) technology. Each major version of the Windows API has a distinct name that identifies a compatibility aspect of that version. For example, Win32

164-544: 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

246-420: 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

328-496: 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

410-517: A DLL file called commctrl.dll on 16-bit Windows, and comctl32.dll on 32-bit Windows. It is grouped under the User Interface category of the API. The Windows Shell component provides access to the operating system shell . The component resides in shell.dll on 16-bit Windows, and shell32.dll on 32-bit Windows. The Shell Lightweight Utility Functions are in shlwapi.dll . It is grouped under

492-449: 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

574-517: 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

656-411: 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

738-523: A compiler that could produce the code needed for these thunks. Versions of 64-bit Windows are also able to run 32-bit applications via WoW64 . The SysWOW64 folder located in the Windows folder on the OS drive contains several tools to support 32-bit applications. Each version of Microsoft Windows contains a version of Windows API, and almost every new version of Microsoft Windows has introduced additions and changes to

820-534: A complex scheme of API thunks was used that could allow 32-bit code to call into 16-bit code (for most of Win16 APIs) and vice versa. Flat thunks allowed 32-bit code to call into 16-bit libraries, and the scheme was used extensively inside Windows 95's libraries to avoid porting the whole OS to Win32 in one batch. In Windows NT, the OS was pure 32-bit, except parts for compatibility with 16-bit applications, and only generic thunks were available to thunk from Win16 to Win32, as for Windows 95. The Platform SDK shipped with

902-435: 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

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984-524: 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

1066-441: 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

1148-470: 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

1230-470: A personal failure." One of the largest changes to the Windows API was the transition from Win16 (shipped in Windows 3.1 and older) to Win32 (Windows NT and Windows 95 and up). While Win32 was originally introduced with Windows NT 3.1 and Win32s allowed use of a Win32 subset before Windows 95, it was not until Windows 95 that widespread porting of applications to Win32 began. To ease the transition, in Windows 95, for developers outside and inside Microsoft,

1312-440: 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)

1394-643: 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

1476-404: 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

1558-441: 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

1640-400: A system of commands and thereby bar all others from writing its different versions to carry out all or part of the same commands. Remote procedure call In distributed computing , a remote procedure call ( RPC ) is when a computer program causes a procedure (subroutine) to execute in a different address space (commonly on another computer on a shared computer network ), which

1722-454: 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

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1804-430: 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

1886-512: 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

1968-516: 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

2050-562: Is debatable since they don't provide or expose all of the capabilities of Windows API. Although almost all Windows programs use the Windows API, on the Windows NT line of operating systems, programs that start early in the Windows startup process use the Native API instead. The Windows API has always exposed a large part of the underlying structure of the Windows systems to programmers. This had

2132-399: 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

2214-413: Is important. RPCs are a form of inter-process communication (IPC), in that different processes have different address spaces: if on the same host machine, they have distinct virtual address spaces, even though the physical address space is the same; while if they are on different hosts, the physical address space is also different. Many different (often incompatible) technologies have been used to implement

2296-568: Is not intended to be used directly by 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

2378-453: 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

2460-490: Is provided by win32k.sys which communicates directly with the graphics driver. The User Interface component provides features to create and manage screen windows and most basic controls, such as buttons and scrollbars , receive mouse and keyboard input, and other functions associated with the graphical user interface (GUI) part of Windows. This functional unit resides in user.exe on 16-bit Windows, and user32.dll on 32-bit Windows. Since Windows XP versions,

2542-469: 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

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2624-447: Is the major version of Windows API that runs on 32-bit systems. The name, Windows API, collectively refers to all versions of this capability of Windows. Microsoft provides developer support via a software development kit , Microsoft Windows SDK , which includes documentation and tools for building software based on the Windows API. This section lists notable services provided by the Windows API. Base services include features such as

2706-455: Is thrown, the kernel and base libraries unwind the stack running handlers and filters as they are encountered. Eventually, every exception unhandled by the application will be dealt with by the default backstop handler, which pops up the Windows common crash dialog. API 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

2788-440: 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

2870-433: Is written as if it were a normal (local) procedure call, without the programmer explicitly writing the details for the remote interaction. That is, the programmer writes essentially the same code whether the subroutine is local to the executing program, or remote. This is a form of client–server interaction (caller is client , executor is server ), typically implemented via a request–response message passing system. In

2952-539: 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

3034-682: 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

3116-501: 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

3198-535: 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

3280-400: The User Interface category of the API. Network Services provide access to the various networking abilities of the operating system. Its subcomponents include NetBIOS , Winsock , NetDDE , remote procedure call (RPC) and many more. This component resides in netapi32.dll on 32-bit Windows. The Internet Explorer (IE) web browser exposes APIs and as such could be considered part of

3362-429: The file system , devices , processes , threads , and error handling . These functions reside in kernel.exe , krnl286.exe or krnl386.exe files on 16-bit Windows, and kernel32.dll and KernelBase.dll on 32 and 64 bit Windows. These files reside in the folder \Windows\System32 on all versions of Windows. Advanced services include features beyond the kernel like the Windows registry , shutdown/restart

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3444-479: 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

3526-444: The object-oriented programming paradigm, RPCs are represented by remote method invocation (RMI). The RPC model implies a level of location transparency, namely that calling procedures are largely the same whether they are local or remote, but usually, they are not identical, so local calls can be distinguished from remote calls. Remote calls are usually orders of magnitude slower and less reliable than local calls, so distinguishing them

3608-456: 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

3690-489: 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

3772-496: 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

3854-581: The Platform SDK. Flat assembler FASM allows building Windows programs without using an external linker, even when running on Linux. Windows specific compiler support is also needed for Structured Exception Handling (SEH). This system serves two purposes: it provides a substrate on which language-specific exception handling can be implemented, and it is how the kernel notifies applications of exceptional conditions such as dereferencing an invalid pointer or stack overflow. The Microsoft/Borland C++ compilers had

3936-480: The RC 4000 multiprogramming system, which used a request-response communication protocol for process synchronization. The idea of treating network operations as remote procedure calls goes back at least to the 1970s in early ARPANET documents. In 1978, Per Brinch Hansen proposed Distributed Processes, a language for distributed computing based on "external requests" consisting of procedure calls between processes. One of

4018-518: The Win32-specific DLLs simple. LCC-Win32 is a C compiler maintained by Jacob Navia, freeware for non-commercial use. Pelles C is a freeware C compiler maintained by Pelle Orinius. Free Pascal is a free software Object Pascal compiler that supports the Windows API. The MASM32 package is a mature project providing support for the Windows API under Microsoft Macro Assembler (MASM) by using custom made or converted headers and libraries from

4100-639: The Windows API and the WinRT API, which is implemented in C++ and is object-oriented by design. Windows.pas is a Delphi unit that exposes the features of Windows API – the Pascal equivalent of windows.h . Many Microsoft technologies use the Windows API -- as most software running on Windows does. As middle-ware between Windows API and an application, the following technologies provide some access to Windows API. Some technologies are described as wrapping Windows API, but this

4182-748: The Windows API bindingly. To develop software that uses the Windows API, a compiler must be able to use the Microsoft-specific DLLs listed above (COM-objects are outside Win32 and assume a certain vtable layout). The compiler must either handle the header files that expose the interior API function names, or supply such files. For the language C++, Zortech (later Symantec , then Digital Mars ), Watcom and Borland have all produced well known commercial compilers that have been used often with Win16, Win32s, and Win32. Some of them supplied memory extenders , allowing Win32 programs to run on Win16 with Microsoft's redistributable Win32s DLL. The Zortech compiler

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4264-442: The Windows API support thousands. However, in general, the interface remained fairly consistent, and an old Windows 1.0 application will still look familiar to a programmer who is used to the modern Windows API. Microsoft has made an effort to maintain backward compatibility . To achieve this, when developing new versions of Windows, Microsoft sometimes implemented workarounds to allow compatibility with third-party software that used

4346-545: The Windows API to allow executing simple Windows programs from a DOS command line. Odin is a project to emulate Win32 on OS/2 , superseding the original Win-OS/2 emulation which was based on Microsoft code. Other minor implementations include the MEWEL and Zinc libraries which were intended to implement a subset of the Win16 API on DOS (see List of platform-independent GUI libraries ). Windows Interface Source Environment (WISE)

4428-415: The Windows API. The name, Windows API, refers to essentially the same capability in each version of Windows, but there is another name for this capability that is based on major architectural aspects of the Windows version that contains it. When there was only one version, it was simply called Windows API. Then, when the first major update was made, Microsoft gave it the name Win32 and gave the first version

4510-477: The Windows API. IE has been included with the operating system since Windows 95 OSR2 and has provided web-related services to applications since Windows 98 . The Windows API is a C language -based API. Functions and data structures are consumable via C syntax by including windows.h , but the API can be consumed via any programming language that can inter-operate with the API data structures and calling conventions for function calls and callbacks . Of note,

4592-527: The Windows hello-world program." Petzold explains that while it was the first Windows sample programs developers were introduced to, it was quite "fancy" and more complex than needed. Tired of people ridiculing the length of the sample, he eventually reduced it to a simple MessageBox call. Over the years, various changes and additions were made to Windows systems, and the Windows API changed and grew to reflect this. The Windows API for Windows 1.0 supported fewer than 450 function calls , whereas modern versions of

4674-454: The ability to use this system as soon as it was introduced in Windows 95 and NT, however the actual implementation was undocumented and had to be reverse engineered for the Wine project and free compilers. SEH is based on pushing exception handler frames onto the stack, then adding them to a linked list stored in thread-local storage (the first field of the thread environment block). When an exception

4756-426: The advantage of giving them much flexibility and power over their applications, but also creates great responsibility in how applications handle various low-level, sometimes tedious, operations that are associated with a graphical user interface . For example, a beginning C programmer will often write the simple "hello world" as their first assignment. The working part of the program is only a single printf line within

4838-401: 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

4920-576: The basic controls reside in comctl32.dll , together with the common controls (Common Control Library). The Common Dialog Box Library provides standard dialog boxes to open and save files, choose color and font, etc. The library resides in a file called commdlg.dll on 16-bit Windows, and comdlg32.dll on 32-bit Windows. It is grouped under the User Interface category of the API. The Common Control Library provides access to advanced user interface controls include things like status bars , progress bars , toolbars and tabs . The library resides in

5002-413: 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

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5084-434: The concept. Request–response protocols date to early distributed computing in the late 1960s, theoretical proposals of remote procedure calls as the model of network operations date to the 1970s, and practical implementations date to the early 1980s. Bruce Jay Nelson is generally credited with coining the term "remote procedure call" in 1981. Remote procedure calls used in modern operating systems trace their roots back to

5166-463: The earliest practical implementations was in 1982 by Brian Randell and colleagues for their Newcastle Connection between UNIX machines. This was soon followed by "Lupine" by Andrew Birrell and Bruce Nelson in the Cedar environment at Xerox PARC . Lupine automatically generated stubs, providing type-safe bindings, and used an efficient protocol for communication. One of the first business uses of RPC

5248-420: 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

5330-476: 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

5412-490: 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

5494-503: The implementation of API functions has been developed in several languages other than C. Despite the fact that C is not an object-oriented programming (OOP) language, the Windows API is somewhat object-oriented due to its use of handles. Various other technologies from Microsoft and others make this object-oriented aspect more apparent by using an OOP language such as C++ -- see Microsoft Foundation Class Library (MFC), Visual Component Library (VCL), GDI+ . Of note, Windows 8 provides

5576-499: The main subroutine. The overhead for linking to the standard I/O library is also only one line: Charles Petzold , who wrote several books about programming for the Windows API, said: "The original hello world program in the Windows 1.0 SDK was a bit of a scandal. HELLO.C was about 150 lines long, and the HELLO.RC resource script had another 20 or so more lines. (...) Veteran programmers often curled up in horror or laughter when encountering

5658-500: The name Win16. The term Windows API refers to both versions and all subsequently developed major versions. The Wine project provides a Win32 API compatibility layer for Unix-like platforms, between Linux kernel API and programs written for the Windows API. ReactOS goes a step further and aims to implement the full Windows operating system, working closely with the Wine project to promote code re-use and compatibility. DosWin32 and HX DOS Extender are other projects which emulate

5740-571: The only integrated development environments (IDEs) that could provide this (although, the SDK is downloadable for free separately from the entire IDE suite, from Microsoft Windows SDK for Windows 7 and .NET Framework 4 ). As of 2016, the MinGW and Cygwin projects also provide such an environment based on the GNU Compiler Collection (GCC), using a stand-alone header file set, to make linking against

5822-473: The prior version in an undocumented or even inadvisable way. Raymond Chen , a Microsoft developer who works on the Windows API, has said: "I could probably write for months solely about bad things apps do and what we had to do to get them to work again (often in spite of themselves). Which is why I get particularly furious when people accuse Microsoft of maliciously breaking applications during OS upgrades. If any application failed to run on Windows 95, I took it as

5904-595: 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

5986-466: The remote procedure was actually invoked. Idempotent procedures (those that have no additional effects if called more than once) are easily handled, but enough difficulties remain that code to call remote procedures is often confined to carefully written low-level subsystems. To let different clients access servers, a number of standardized RPC systems have been created. Most of these use an interface description language (IDL) to let various platforms call

6068-442: 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

6150-415: The rise of the internet, particularly in the 2000s. RPC is a request–response protocol. An RPC is initiated by the client , which sends a request message to a known remote server to execute a specified procedure with supplied parameters. The remote server sends a response to the client, and the application continues its process. While the server is processing the call, the client is blocked (it waits until

6232-510: The server has finished processing before resuming execution), unless the client sends an asynchronous request to the server, such as an XMLHttpRequest. There are many variations and subtleties in various implementations, resulting in a variety of different (incompatible) RPC protocols. An important difference between remote procedure calls and local calls is that remote calls can fail because of unpredictable network problems. Also, callers generally must deal with such failures without knowing whether

6314-448: 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

6396-440: The system (or abort), start/stop/create a Windows service , manage user accounts. These functions reside in advapi32.dll and advapires32.dll on 32-bit Windows. The Graphics Device Interface (GDI) component provides features to output graphics content to monitors , printers , and other output devices . It resides in gdi.exe on 16-bit Windows, and gdi32.dll on 32-bit Windows in user-mode. Kernel-mode GDI support

6478-561: Was a licensing program from Microsoft which allowed developers to recompile and run Windows-based applications on Unix and Macintosh platforms. WISE SDKs were based on an emulator of the Windows API that could run on those platforms. Efforts toward standardization included Sun's Public Windows Interface (PWI) for Win16 (see also: Sun Windows Application Binary Interface ( Wabi )), Willows Software's Application Programming Interface for Windows (APIW) for Win16 and Win32 (see also: Willows TWIN ), and ECMA-234 , which attempted to standardize

6560-555: Was by Xerox under the name "Courier" in 1981. The first popular implementation of RPC on Unix was Sun's RPC (now called ONC RPC), used as the basis for Network File System (NFS). In the 1990s, with the popularity of object-oriented programming , an alternative model of remote method invocation (RMI) was widely implemented, such as in Common Object Request Broker Architecture (CORBA, 1991) and Java remote method invocation. RMIs, in turn, fell in popularity with

6642-455: 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

6724-602: Was probably one of the first stable and usable C++ compilers for Windows programming, before Microsoft had a C++ compiler. For certain classes of applications, the compiler system should also be able to handle interface description language (IDL) files. Collectively, these prerequisites (compilers, tools, libraries, and headers) are known as the Microsoft Platform SDK . For a time, the Microsoft Visual Studio and Borland 's integrated development system were

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