Components of .Net Framework

Common Language Runtime

CLR is the heart of .Net Framework.

CLR is one of the key components of .Net Framework. CLR is the core runtime engine in the Microsoft .NET Framework for executing all kinds of applications.

Execution environment for code written in .NET Framework.

The CLR is described as the "execution engine" of .NET. It is this CLR that manages the execution of programs. It provides the environment within which the programs run. The software version

of .NET is actually the CLR version.

The CLR works with every language available for the .NET Framework.

The CLR is a multi-language execution environment. There are currently over 15 compilers being built by Microsoft and other companies producing code that will execute in CLR.

But CLR is not a common compiler for all .NET compatible languages.

We all know that .Net framework supports 70+ languages. But, since CLR is mentioned as the “execution engine” of .Net framework, it is not a common compiler for all language that converts the source code of any language to Machine code or Managed code.

Note: All .Net compatible languages have their own compiler. (i.e.) all 70+ languages have their own compiler.

Common Type System

CTS describes a set of types (Data Types) that can be used in different .Net languages in common. (i.e), CTS ensures that objects written in different .Net languages can interact with each other.

For Communicating between programs written in any .NET complaint language, the types have to be compatible on the basic level.

The common type system supports two general categories of types:

Value types:

Value types directly contain their data, and instances of value types are either allocated on the stack or allocated inline in a structure. Value types can be built-in (implemented by the runtime), user-defined, or enumerations.

Reference types:

Reference types store a reference to the value's memory address, and are allocated on the heap. Reference types can be self-describing types, pointer types, or interface types. The type of a reference type can be determined from values of self-describing types. Self-describing types are further split into arrays and class types. The class types are user-defined classes, boxed value types, and delegates.

Common Language Specification

Common Language Specification is a sub set of CTS.

CLS specifies a set of rules that needs to be adhered or satisfied by all language compilers targeting CLR.

CLS helps in cross language inheritance and cross language debugging.

Common language specification rules:

It describe the minimal and complete set of features to produce code that can be hosted by CLR 

It ensure that products of compilers will work properly in .NET environment 

Sample rules: 

Representation of text strings 

Internal representation of enumerations 

Definition of static members and this is a subset of the CTS which all .NET languages are expected to support.

Microsoft has defined CLS which are nothing but guidelines that language to follow so that it can communicate with other .NET languages in a seamless manner.

Base Class Library

Also called as Framework Class Library.

BCL are similar to header file in other programming languages.

BCL are set of predefined code available for all languages supporting .Net Framework

Developers just need to import the BCL in their language code and use its predefined methods and properties to implement common and complex functions like reading and writing to file, graphic rendering, database interaction, and XML document manipulation.