Cygwin's default user interface will be the bash shell operating inside the mintty terminal emulator.[25] The DLL also implements pseudo terminal (pty) gadgets, and Cygwin ships with numerous terminal emulators which can be depending on them, like rxvt/urxvt and xterm. The Edition of GCC that includes Cygwin has different extensions https://acgwin31740.blogolize.com/acgwin-no-further-a-mystery-76145548