Cygwin's default person interface is the bash shell running within the mintty terminal emulator.[25] The DLL also implements pseudo terminal (pty) gadgets, and Cygwin ships with numerous terminal emulators which are depending on them, which includes rxvt/urxvt and xterm. The Edition of GCC that comes with Cygwin has numerous extensions https://acgwin85184.bligblogging.com/37827150/acgwin-fundamentals-explained