## 29.1. WSI Platform

A platform is an abstraction for a window system, OS, etc. Some examples include MS Windows, Android, and Wayland. The Vulkan API may be integrated in a unique manner for each platform.

The Vulkan API does not define any type of platform object. Platform-specific WSI extensions are defined, which contain platform-specific functions for using WSI. Use of these extensions is guarded by preprocessor symbols as defined in the Window System-Specific Header Control appendix.

In order for an application to be compiled to use WSI with a given platform, it must #define the appropriate preprocessor symbol prior to including the "vulkan.h" header file. Each platform-specific extension is an instance extension. The application must enable instance extensions with `vkCreateInstance` before using them.