Question : Cisco Switch - spanning tree command

I have two of the same switches
Cisco Catalayst 2950

One of them takes the following commands, while the other one doesn't

spanning-tree mode pvst
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id

I get the following error on switch 2, which is supposed to work as the backup for switch1

Switch2(config)#spanning-tree mode pvst
                                               ^
% Invalid input detected at '^' marker.

Please tell me how I can issue the three spanning-tree commands to the second switch.
Thanks,

Answer : Cisco Switch - spanning tree command

Different versions of IOS have different feature sets available.

Upgrading IOS is very, very easy.

To determine the version of IOS that you need for a specific feature refer to the Feature Navigator
http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp

To download the current IOS use the Upgrade Planner
http://www.cisco.com/cgi-bin/Software/Iosplanner/Planner-tool/iosplanner.cgi