The following text from a book:
Default arguments are useful if you don’t want to go to the trouble of writing arguments that, for example, almost always have the same value. They are also useful in cases where, after a program is written, the programmer decides to increase the capability of a function by adding another argument. Using default arguments means that the existing function calls can continue to use the old number of arguments, while new function calls can use more.
Could you please explain it to me? I couldn't understand it. It would be really kind of you. Perhaps a simple example would make it clear.