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What is SDK and the system introduction

Time:2021.08.07     Author:sertag

   SDK (software development kit) is a collection of development tools used by software engineers to create application software for specific software packages, software frameworks, hardware platforms, operating systems, etc. It can simply provide some files of application program interface API for a programming language, but it may also include complex hardware that can communicate with an embedded system. SDKs also often include sample code, supporting technical notes, or other supporting documentation to clarify doubts about basic resources.
   In the beginning, the API collection is called SDK. For example, the API collection provided by MAC is called MAC SDK. With the evolution of time, the current SDK refers to the middleware with one group of APIs as input and another group of APIs as output. For example, sertag's ESL system provides a set of APIs in the form of HTTP requests. Since it is troublesome to construct HTTP requests nowadays, there are gradually "SDKs" for various systems. This SDK encapsulates the HTTP interface of the ESL system and provides a set of objective C or swift interfaces.
  The relationship between the system and SDK. DLL (dynamic link library, format. DLL) in Windows system is also an executable file format. Unlike. Exe files,. DLL files cannot be executed directly. They are usually imported by. Exe when executing, and contain some resources and executable code (execution code of API functions). In order to use API functions in DLL, we must have API function declaration (. H) and its import library (. LIB). The import library is used to find the entry point of API in DLL. Therefore, in order to use API functions, we need to have. H and. Lib files corresponding to the API, and the SDK provides a complete set of relevant files, examples and tools for developing Windows applications. Because SDK contains the necessary materials for using API, people often call the development method of using API only to write Windows applications SDK programming.
   IOS (URL scheme) is a closed sandbox selected by apple to protect users' privacy and security. App can only access its own sandbox, but it also hinders the reasonable information sharing between applications. Sandbox is a security system, which stipulates that an application can only read files in the folder created for the application, and can not access the contents of other places. All non code files are saved in this place, such as pictures, sounds, attribute lists, text files, etc. The application realizes the transmission of information through the URL scheme designed by each app that conforms to Apple's unified specification. URL scheme is designed to facilitate calls between apps. If an app needs to provide a function or data for other apps to access, a corresponding URL scheme must be defined in the app. You can open the app through the OpenURL of the system through a url like link, and you can pass some parameters. Each URL must uniquely identify an app. If the URL you set conflicts with the URL of other apps, your app may not be called at this time because the URL of this app has been registered in the system when the app is  Scheme. If your are consistent but installed later, the system will not call your app because the URL scheme set by your app is overwritten.
  To develop android app on the Android platform, we must download the Android SDK from the official website, and then use the API provided by this SDK to call system capabilities. For example, I use Android   SDK to call the function that the system screen is always on. Without this tool provided by this toolbox, this function cannot be realized.