Cygwin's default user interface will be the bash shell working inside the mintty terminal emulator.[25] The DLL also implements pseudo terminal (pty) gadgets, and Cygwin ships with several terminal emulators which can be determined by them, like rxvt/urxvt and xterm. The Model of GCC that includes Cygwin has different extensions https://acgwin19529.bloggactivo.com/36325275/details-fiction-and-acgwin