C can obviously parse flags. See for example the plethora of C software that does so, such as many things from GNU Coreutils. There is no requirement to parse

C can obviously parse flags. See for example the plethora of C software that does so, such as many things from GNU Coreutils. There is no requirement to parse flags for the basic functionality of yes. You implemented that yourself. You can remove your own requirement whenever you want. You don't need to parse a flag, at most you need to parse a string from the command line arguments. I wonder at this point how you define "flag".