https://supportforums.cisco.com/discussion/10513706/setting-boot-system-commands
show boot
TRUE link
http://www.cisco.com/c/en/us/support/docs/switches/catalyst-2950-series-switches/41845-192.html
Here is an example:
Switch#show boot2955#configure terminal 2955(config)#boot system flash:c2955-i6q4l2-mz.121-13.EA1.bin