If you don't specify a return type then the compiler assumes it is int. I'm not sure why your program compiles in VS; it should at least give a warning that you aren't returning a value.
The moral is that you really ought to specify a return type for all functions, even if it is void. C has evolved a lot since Ritchie's book, so don't stick to everything he does religiously. Listen to what you are taught. Study all the compiler warnings and try to ensure that you deal with the causes of all of them.