Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache.
The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer.
The Global Assembly Cache (GAC) is a folder in Windows directory to store the .NET assemblies that are specifically designated to be shared by all applications executed on a system.
Starting with the .NET Framework 4, the default location for the global assembly cache is %windir%\Microsoft.NET\assembly.
In earlier versions of the .NET Framework, the default location is %windir%\assembly.