API: Application Program Interface (API: Application Program Interface)

Application programming interface (API: application programming interface) is a set of definitions, procedures and protocols, through the API interface Realize mutual communication between computer software. A primary function of an API is to provide a common feature set. Programmers can ease programming tasks by developing applications using API functions, thereby avoiding writing useless programs.

API is also a kind of middleware that provides data sharing for various platforms. Based on the performance of data sharing between different software applications on a single or distributed platform, APIs can be divided into four types:

Remote Procedure Call (RPC): Sharing through functions Procedures (or tasks) on the data buffer implement inter-program communication.

Standard Query Language (SQL): It is a standard query language for accessing data, and realizes data sharing between applications through a universal database.

File transfer: File transfer enables data sharing between applications by sending formatted files.

Information delivery: refers to small formatted information between loosely coupled or tightly coupled applications, and data sharing is achieved through direct communication between programs.

Current standards applied to APIs include the ANSI Standard SQL API. There are also standards that are being developed for other types of applications. The API can be used on all computer platforms and operating systems. These APIs connect data in different formats (such as shared data caches, database structures, file frames). Each data format requires different data commands and parameters for correct data communication, but also produces different types of errors. Therefore, in addition to having the knowledge required to perform data sharing tasks, these types of APIs must also address many network parameter issues and possible error conditions, that is, each application must know whether it has strong performance support procedures. communication between. In contrast, because this API handles only one message format, the message delivery API in this case only provides a smaller subset of commands, network parameters, and error conditions. Because of this, the delivery API method greatly reduces system complexity, so when an application needs to share data through multiple platforms, the information delivery API type is an ideal choice.

API is distinctly different from graphical user interface (GUI) or command interface: API interface belongs to an operating system or program interface, while the latter two are direct user interfaces.

Sometimes companies use APIs as their public open systems. That is to say, the company formulates its own system interface standard. When it is necessary to perform operations such as system integration, customization, and program application, all members of the company can call the source code through this interface standard. This interface standard is called an open API. .