If you didn't have an entry in the DNS (Domain Name System) or the hosts file for a particular hostname, and yet you're still able to resolve the IP address, it's possible that the resolution is happening through other means such as NetBIOS name resolution or local network broadcasts.

In Windows, NetBIOS (Network Basic Input/Output System) is a legacy networking protocol that provides a way to resolve computer names to IP addresses within a local network. It uses broadcasts and name resolution protocols like NBNS (NetBIOS Name Service) to resolve names.

When you try to resolve a hostname using functions like getnameinfo, the operating system may use various methods to perform the resolution. It may first check the DNS, then the hosts file, and if those fail, it may fall back to other methods like NetBIOS name resolution.

If you're observing hostname resolution even without DNS or hosts file entries, it's likely that your network environment or the specific configuration of your system allows for alternative name resolution methods like NetBIOS.

Relying on such mechanisms may not always provide consistent and reliable results, especially in larger or more complex network environments. It's generally recommended to have proper DNS or hosts file entries for accurate and predictable hostname resolution.