.NET Framework (pronounced dot net) is a software framework developed by Microsoft that runs primarily on Microsoft Windows. It includes a large class library known as Framework Class Library (FCL) and provides language interoperability (each language can use code written in other languages) across several programming languages. Programs written for .NET Framework execute in a software environment (as contrasted to hardware environment), known as Common Language Runtime (CLR), an application virtual machine that provides services such as security, memory management, and exception handling. FCL and CLR together constitute .NET Framework.
FCL provides user interface, data access, database connectivity, cryptography, web application development, numeric algorithms, and network communications. Programmers produce software by combining their own source code with .NET Framework and other libraries. .NET Framework is intended to be used by most new applications created for Windows platform. Microsoft also produces an integrated development environment largely for .NET software called Visual Studio.
.NET Framework started out as a proprietary framework, although the company worked to standardize the software stack almost immediately, even before its first release. Despite the standardization efforts, developers—particularly those in the free and open-source software communities—expressed their uneasiness with the selected terms and the prospects of any free and open-source implementation, especially with regard to software patents. Since then, Microsoft has changed .NET development to more closely follow a contemporary model of a community-developed software project, including issuing an update to its patent promises to address the concerns.