Microsoft C Runtime -

Microsoft C Runtime (CRT) is a critical collection of libraries and routines that support program development in the C and C++ languages. It provides the low-level building blocks—such as memory management, file handling, and math functions—that applications need to run on the Windows operating system. Core Components

Language/C++ Standard Library

(if using C++):

  • Compiler support functions: exception handling, C++ new/delete, stack unwinding, typeid, thread-local storage (TLS), atexit.
  • Entry point (mainCRTStartup, wmainCRTStartup).

do not uninstall them

It is tempting to "clean up" the dozens of redistributables in your Control Panel, but unless you are troubleshooting a specific issue. Removing an old 2008 version might break an older printer driver or a classic game that still relies on that specific "instruction manual". microsoft c runtime

  • C99/C11 gaps – Missing tgmath.h, complex.h for many complex functions, aligned_alloc (added later), timespec_get, and full threads.h support.
  • ABI & version hell – Different CRT versions (v100, v110, v120, v140, v142) incompatible with each other; mixing leads to crashes or heap corruption.
  • Large binary overhead – Static linking (/MT) embeds a copy into every EXE; dynamic linking (/MD) requires distributing vcruntime140.dll.
  • Licensing – Redistributable but requires proper deployment; older MSVCRT from Windows system folder cannot be used for new apps.
  • Modern C++ friction – It's a C library; iostreams and std::string are separate, and mixing malloc with new without care causes trouble.
  • No cross-platform friendliness – Not portable to Linux/macOS without Wine; _open vs open, _fseeki64 instead of fseeko.