n cin.ignore()
what if you did
cin.ignore(5, '\n');
and the user entered

abcdefghij

that would be over 5.  But this would only ignore 5 characters

so the programmer used
cin.ignore(10, '\n');
and the user entered
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

and it still doesn't cover what the user entered

so the programmer used
cin.ignore(20,'\n');
and the user entered
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

still not enough

so my question is, if you never can predict what the user is going to enter,
how do you even come close to picking the numeric that is needed within ignore?

ignore will work in some case and fail in other
why would you pick code that could fail in some cases?
not good coding?

you need code that will work exactly as you want in all cases

and that would NOT be with ignore

so what will work in all cases?