NGEN

A managed executable can be precompiled from IL to the native code, using the NGEN utility. You can do this when the executable is expected to run repeatedly from a local disk, to save time on just-in-time compilation. This is standard procedure, for example, for managed components of the .NET Framework, which are precompiled during the installation. (Tom Archer refers to this as install-time code generation.) In this case, the precompiled code is saved to the local disk or other storage, and every time the executable is invoked, the precompiled native-code version is used instead of the original IL version. The original file, however, must also be present because the precompiled version does not carry the metadata.