Regardless of the programming language, the resulting program operates internally on data types; therefore, the CLI includes the Common Type System (CTS). The CTS defines how types are structured and laid out in memory, as well as the concepts and behaviors that surround types. It includes type manipulation directives alongside the information about the data stored within the type. The CTS standard applies to how types appear and behave at the external boundary of a language because the purpose of the CTS is to achieve interoperability between languages. It is the responsibility of the runtime at execution time to enforce the contracts established by the CTS.
Within the CTS, types are broken down into two categories.
These two categories of types translate directly to C# syntax that provides a means of declaring each type.