What does API mean?

API (Application Programming Interface) is some predefined functions, whose purpose is to provide applications and developers with the ability to access a set of routines based on certain software or hardware, without accessing the source code or knowing the details of the internal working mechanism.

Classification:

Windows API:

The API function is contained in the dynamic link library file under the Windows system directory. Windows API is a set of predefined Windows functions, which are used to control the appearance and behavior of various Windows components. Every action of the user will cause one or several functions to run to tell Windows what happened. This is very similar to the natural code of Windows to some extent. Other languages just provide an automatic and easy way to access the API. When you click a button on the form, Windows will send a message to the form, and VB will get this call and generate a specific event after analysis.

It is easier to understand that Windows system is not only a great service center, but also coordinates the execution of application programs, the allocation of memory and the management of system resources. Calling various services in this service center (each service is a function) can help applications open windows, draw graphics and use peripherals. Because these functions serve applications, they are called application programming interfaces, or API functions for short. WIN32 API is the application programming interface of MicrosoftWindows 32-bit platform.

Any application executing in Windows working environment can call Windows API.

linux API:

In linux, the user programming interface API follows the-POSIX standard, which is the most popular application programming interface standard in UNIX. POSIX standard is a standard system jointly developed by IEEE and ISO/IEC. Based on the existing UNIX practice and experience at that time, the standard describes the system call programming interface API of the operating system, which is used to ensure that the application program can be transplanted and run on various operating systems at the source program level. These system call programming interfaces are mainly implemented by C Library (LIBC).