The "msvcp100d.dll" file is a component of the Microsoft Visual Studio 2010, which is developed and provided by Microsoft Corporation. This particular dynamic link library (DLL) is associated with the debug version of the Microsoft C Runtime Library. The name itself provides some insight into its purpose: "msvcp" stands for Microsoft Visual C++ and the "100" indicates that it's related to Visual Studio 2010, while the "d" at the end specifies that it's the debug version. In the context of software development, particularly when working with C++ in Visual Studio, the runtime library plays a pivotal role. It comprises routines and program instructions that programs, especially those written in C++, use at runtime. The debug version of this library provides additional diagnostic and tracking capabilities to assist developers in identifying, isolating, and resolving potential issues during the software development phase.

To put it simply, when developers write and test their applications in a debug mode within Visual Studio 2010, this DLL provides the necessary runtime functionalities. If this DLL is missing or corrupted, it could lead to errors, especially when attempting to run or debug C++ programs in the specified environment. It's essential for developers to ensure they have the correct versions of these DLLs, especially when distributing software, to avoid runtime issues.