The `msvcp120_clr0400.dll` is a dynamic link library (DLL) file associated with Microsoft Visual Studio 2013, specifically as part of the Microsoft C Runtime Library. This DLL is crucial for applications developed with Visual Studio 2013 that use C++ and .NET Framework 4.0, as indicated by the "clr0400" in the filename. The "msvcp" prefix stands for Microsoft Visual C++ and the "120" signifies the version of the C++ runtime library that corresponds to Visual Studio 2013. This file is essential for running C++ applications built with Visual Studio 2013 that target the .NET Framework 4.0, as it contains standard C++ library functions implemented for the .NET environment. These functions can include operations related to input/output processing, string manipulation, and memory management among others. The presence of this DLL ensures that the applications have the necessary components to execute properly in a .NET framework environment.

If `msvcp120_clr0400.dll` is missing or corrupted, it may lead to runtime errors or the application failing to start, as the required runtime components are unavailable. Resolving such issues typically involves reinstalling the Microsoft Visual C++ Redistributable Packages for Visual Studio 2013, which would include the `msvcp120_clr0400.dll` and other necessary DLLs. It's also advisable to ensure that the .NET Framework 4.0 is properly installed and updated on the system, as it's a prerequisite for applications that rely on this particular DLL.