The Common Language Infrastructure (CLI) is an open

specification A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard. There are different types of technical or engineering specificati ...

and

technical standard A technical standard is an established Social norm, norm or requirement for a repeatable technical task which is applied to a common and repeated use of rules, conditions, guidelines or characteristics for products or related processes and producti ...

originally developed by

Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...

and standardized by

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

IEC The International Electrotechnical Commission (IEC; ) is an international standards organization that prepares and publishes international standards for all electrical, electronic and related technologies. IEC standards cover a vast range of ...

(ISO/IEC 23271) and

Ecma International Ecma International () is a Nonprofit organization, nonprofit standards organization for information and communication systems. It acquired its current name in 1994, when the European Computer Manufacturers Association (ECMA) changed its name to ...

(ECMA 335) that describes executable code and a runtime environment that allows multiple high-level languages to be used on different computer platforms without being rewritten for specific architectures. This implies it is platform agnostic. The .NET Framework,

.NET The .NET platform (pronounced as "''dot net"'') is a free and open-source, managed code, managed computer software framework for Microsoft Windows, Windows, Linux, and macOS operating systems. The project is mainly developed by Microsoft emplo ...

and Mono are implementations of the CLI. The

metadata Metadata (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive ...

format is also used to specify the

API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...

definitions exposed by the

Windows Runtime Windows Runtime (WinRT) is a platform-agnostic component and application architecture first introduced in Windows 8 and Windows Server 2012 in 2012. It is implemented in C++ and officially supports development in C++ (via C++/WinRT, C++/CX ...

Overview

Among other things, the CLI specification describes the following five aspects: ;The Common Type System (CTS) :A set of

data type In computer science and computer programming, a data type (or simply type) is a collection or grouping of data values, usually specified by a set of possible values, a set of allowed operations on these values, and/or a representation of these ...

s and operations that are shared by all CTS-compliant

programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...

s. ;The

Metadata Metadata (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive ...

:Information about program structure is language-agnostic, so that it can be referenced between languages and tools, making it easy to work with code written in a language the developer is not using. ;The Common Language Specification (CLS) :The CLS, a subset of the CTS, are rules to which components developed with/for the supported languages must adhere. :They apply to consumers (developers who are programmatically accessing a component that is CLS-compliant), frameworks (developers who are using a language compiler to create CLS-compliant libraries), and extenders (developers who are creating a tool such as a language compiler or a code parser that creates CLS-compliant components). ;The

Virtual Execution System The Virtual Execution System (VES) is a run-time system of the Common Language Infrastructure CLI which provides an environment for executing managed code. It provides direct support for a set of built-in data types, defines a hypothetical mach ...

(VES) :The VES loads and executes CLI-compatible programs, using the metadata to combine separately generated pieces of code at runtime. :All compatible languages compile to

Common Intermediate Language Common Intermediate Language (CIL), formerly called Microsoft Intermediate Language (MSIL) or Intermediate Language (IL), is the intermediate language binary instruction set defined within the Common Language Infrastructure (CLI) specification. ...

(CIL), which is an

intermediate language An intermediate representation (IR) is the data structure or code used internally by a compiler or virtual machine to represent source code. An IR is designed to be conducive to further processing, such as optimization and translation. A "good" ...

that is abstracted from the platform hardware. When the code is executed, the platform-specific VES will compile the CIL to the

machine language In computer programming, machine code is computer code consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). For conventional binary computers, machine code is the binaryOn nonb ...

according to the specific hardware and operating system. :In the CLI standard initially developed by Microsoft, the VES is implemented by the

Common Language Runtime The Common Language Runtime (CLR), the virtual machine component of Microsoft .NET Framework, manages the execution of .NET programs. Just-in-time compilation converts the managed code (compiled intermediate language code) into machine instr ...

(CLR). ;The Standard Libraries :A set of libraries providing many common functions, such as file reading and writing. Their core is the

Base Class Library The Standard Libraries are a set of libraries included in the Common Language Infrastructure (CLI) in order to encapsulate many common functions, such as file reading and writing, XML document manipulation, exception handling, application globa ...

(BCL).

Standardization and licensing

In August 2000,

Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company. It was founded by Bill Hewlett and David Packard in 1939 in a one-car garage in Palo Alto, California ...

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...

, and others worked to standardize CLI. By December 2001, it was ratified by the Ecma, with

standardization following in April 2003. Microsoft and its partners hold patents for CLI. Ecma and ISO/IEC require that all patents essential to implementation be made available under " reasonable and non-discriminatory (RAND) terms." It is common for RAND licensing to require some royalty payment, which could be a cause for concern with Mono. , neither Microsoft nor its partners have identified any patents essential to CLI implementations subject to RAND terms. ,

added C# and CLI to the list of specifications that the Microsoft Community Promise applies to, so anyone can safely implement specified editions of the standards without fearing a patent lawsuit from Microsoft. To implement the CLI standard requires conformance to one of the supported and defined profiles of the standard, the minimum of which is the kernel profile. The kernel profile is actually a very small set of types to support in comparison to the well known core library of default .NET installations. However, the conformance clause of the CLI allows for extending the supported profile by adding new methods and types to classes, as well as deriving from new namespaces. But it does not allow for adding new members to interfaces. This means that the features of the CLI can be used and extended, as long as the conforming profile implementation does not change the behavior of a program intended to run on that profile, while allowing for unspecified behavior from programs written specifically for that implementation. In 2012, Ecma and ISO/IEC published the new edition of the CLI standard.

Implementations

* .NET Framework is Microsoft's original commercial implementation of the CLI. It only supports Windows. It was superseded by .NET in November 2020. *

, previously known as .NET Core, is the free and open-source multi-platform successor to .NET Framework, released under the

MIT License The MIT License is a permissive software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts very few restrictions on reuse and therefore has high license compatibility. Unl ...

* .NET Compact Framework is Microsoft's commercial implementation of the CLI for portable devices and

Xbox 360 The Xbox 360 is a home video game console developed by Microsoft. As the successor to the Xbox (console), original Xbox, it is the second console in the Xbox#Consoles, Xbox series. It was officially unveiled on MTV on May 12, 2005, with detail ...

. * .NET Micro Framework is an open source implementation of the CLI for resource-constrained devices. * Mono is an alternative open source implementation of CLI and accompanying technologies, mainly used for mobile and game development. *

DotGNU DotGNU is a decommissioned part of the GNU Project that started in January 2001 and aimed to provide a free software replacement for Microsoft's .NET Framework. The DotGNU project was run by the Free Software Foundation. Other goals of the proj ...

is a decommissioned part of the GNU Project started in January 2001 that aimed to provide a

free and open source software Free and open-source software (FOSS) is software available under a Software license, license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term ...

alternative to Microsoft's .NET Framework.

Notes

References

* * * *

External links