I am a long time C programmer. I have a large program that is a CAS (computer algebra system). It runs under terminal. It runs fine on Linux and always did on Mac OS. I never bothered to update past OS 10.14 until recently. Since OS 10.15 there is a problem. Reading from the terminal does not work right. Same thing happens on OS 12. Previously one types a command and hits return. But now it won't work unless one hits return three times. Why three works I have no idea. I changed from zsh to bash and it makes no difference. Again, everything is fine on Linux. Any ideas??