Send username for SSH login in PuTTY

If you haven't heard of PuTTY, it is the best SSH/telnet client for Windows available (there is also a Linux version which I haven't tried). I recently got tired of entering a username for one of the accounts I SSH into (it was a random combination of letters and numbers) and was wondering how I could specify that in a PuTTY session config. I could not find that documented anywhere, so I tried the obvious: I put username@hostname under "Host Name (or IP address)" and it worked.