Cisco Commands - Show difference between running config and startup config

Ever wonder exactly what changes have been made to the running config? Should you save them before reloading or would that break everything. Use show archive config differences nvram:startup-config system:running-config to view the difference between the startup config and the current running config.

show archive config differences nvram:startup-config system:running-config

router#show archive config differences nvram:startup-config system:running-config
Contextual Config Diffs:
+ip access-list extended test

120651-149720#

More Info:
http://www.2000trainers.com/cisco-ccna-07/ccna-router-configuration-files/
http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gt_diff.html
http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gt_diff.html#wp1068464