What does api mean?

API is an application programming interface.

API is some predefined interfaces (such as functions, HTTP interface), or refers to the agreement for connecting different components of the software system. A set of routines used to provide applications and developers access to a piece of software or hardware without having to access the source code or understand the details of the inner workings.

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API functions are included in the dynamic link library files in the Windows system directory. The Windows API is a set of predefined Windows functions used to control the appearance and behavior of various components of Windows.

Each user action triggers one or several functions to run to tell Windows what happened. This is somewhat like native Windows code. Other languages ??simply provide an automatic and easier way to access the API.

When a button on the form is clicked, Windows will send a message to the form. VB obtains this call and generates a specific event after analysis.

Reference for the above content? Baidu Encyclopedia—API