In Microsoft's .NET Framework, the Common Type System (CTS) is a standard that specifies how type definitions and specific values of types are represented in computer memory. It is intended to allow programs written in different programming languages to easily share information. As used in programming languages, a type can be described as a definition of a set of values (for example, "all integers between 0 and 10"), and the allowable operations on those values (for example, addition and subtraction).
The specification for the CTS is contained in Ecma standard 335, "Common Language Infrastructure (CLI) Partitions I to VI." The CLI and the CTS were created by Microsoft, and the Microsoft .NET framework is an implementation of the standard.