Common Language Specification (CLS)

The Common Language Specification (CLS) is the set of some basic language features where .Net languages can develop the applications and services, which are compatible with the .Net Framework. If the situation arises of communicating objects which are written in different .Net Complaint languages, then those objects must expose the features that are common to all the languages.

Common Language Specification (CLS) provides the feature of complete interoperability among applications, which is regardless of the language used to create the application.

Common Language Specification (CLS) defines the subset of Common Type System (CTS) and the Common Type System (CTS) describes the set of types that can use different .Net languages are common, it ensure that objects written in different languages can communicate with each other.

Common Type System (CTS)

It describes the set of types which can be used in different .Net languages as common. It ensures that the objects which are written in different .Net languages can communicate with each other. But for the communication between programs that are written in any .NET complaint language, the types would have to be compatible on the basic level.

It supports the object oriented concepts that is why all the types are represented in this as objects and also provides support of sharing of common data types. CTS support two different types: Value and Reference type.

• Value type: The primitive or built in data types of the programming language are known as Value type. It also includes user defined types and enumerations. They are used to store the value of the variable which includes String, Character, Integer, etc. These data types are passed in the method by using by value method. 
• Reference Types: In the reference types they store a reference to the value's memory address, and are allocated on the heap. They can be self-describing types, pointer types, or interface types. Reference types are those whose data type objects are represented by a reference to the object's actual value.