desktopvertexshader.cso

Compiled shader object

A .cso file contains a compiled shader object for DirectX. The shader compiler translates HLSL source code into this binary form at build time. Applications load the compiled shader directly, thus no compilation is necessary at run time. Graphics programs ship .cso files next to their executables. The bytecode targets the Direct3D shader model of the build.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.