What is "windows.h"

windows.h is a Windows-specific header file for the C and C++ programming languages which contains declarations for all of the functions in the Windows API, all the common macros used by Windows programmers, and all the data types used by the various functions and subsystems. It defines a very large number of Windows specific functions that can be used in C. The Win32 API can be added to a C programming project by including the header file and linking to the appropriate libraries. To use functions in xxxx. dll, the program must be linked to xxxx.lib (or libxxxx.dll.a in MinGW). Some headers are not associated with a .dll but with a static library (e.g. scrnsave.h needs scrnsave.lib).