Cygwin, MinGW/MSYS, MinGW-W64/MSYS2

1. Cygwin

http://www.cygwin.com/

Cygwin is a large collection of GNU and Open Source tools which provide functionality similar to a Linux distribution on Windows

Cygwin is a DLL (cygwin1.dll) which provides substantial POSIX API functionality

2. MinGW/MinGW64 (Minimalist GNU for Windows)

https://mingw-w64.org/doku.php
http://www.mingw.org/
https://en.wikipedia.org/wiki/MinGW#Comparison_with_Cygwin

MinGW is a minimalist development environment for native Microsoft Windows applications.

MinGW provides provides a complete Open Source programming tool set which is suitable for the development of native MS-Windows applications, and which do not depend on any 3rd-party C-Runtime DLLs.

3. Msys/Msys2 (Minimal System)

https://github.com/msys2/msys2/wiki

MSYS2 is software distribution and a building platform for Windows. It provides a Unix-like environment, a command-line interface and a software repository making it easier to install, use, build and port software on Windows.

MSYS2 is an independent rewrite of MSYS, based on modern Cygwin and MinGW-w64 with the aim of better interoperability with native Windows software.

The name is a contraction of Minimal SYStem 2, and aims to provide support to facilitate using the bash shell, Autotools, revision control systems and the like for building native Windows applications using MinGW-w64 toolchains.

4. About Msys2, Cygwin, MinGW-w64

https://en.wikipedia.org/wiki/MinGW#Comparison_with_Cygwin
https://github.com/msys2/msys2/wiki/History
https://github.com/msys2/msys2/wiki/How-does-MSYS2-differ-from-Cygwin
https://stackoverflow.com/questions/771756/what-is-the-difference-between-cygwin-and-mingw

Cygwin --fork--> MinGW
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