The resolver often takes the form of a subroutine library that is linked with the application code. In some systems the resolver comes with the operating system (UNIX, Windows 95 etc). In others, it is part of an external TCP/IP package (Winsock, PC-TCP, etc).

When attaching a new host to the network, its resolver needs to be configured with the IP address of one or more nearby name servers, so it knows where to send its DNS queries. On many UNIX systems, this is done by editing the file /etc/resolv.conf.