The Hostname is changed in the configuration mode and you can see the current hostname using the show system hostname command.
If you change the hostname to another, the prompt is changed to the new hostname.
LYSH@MyHostName# show system hostname Hostname : MyHostName LYSH@MyHostName# configure LYSH@MyHostName(config)# hostname set NewHostName LYSH@NewHostName# show system hostname Hostname : NewHostName