Don't you know what OS is installed. If it is windows go to control panel/system. There is written the version of windows.
If it is linux when you startup you see the version. If it is 64bit i suppose it will be shown (not sure).
And at last if you have 32bit cpu you can't install 64bit OS
Use the isalist command to determine whether the machine is running
the 32-bit or 64-bit operating system. If you are running the 64-bit
operating system on an UltraSPARC machine, then isalist will list sparcv9 first
connect to database using sqlplus..will get the result..
default is 32bit..
SQL*Plus: Release 184.108.40.206.0 - Production on Tue Feb 17 15:36:49 2004
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Oracle9i Enterprise Edition Release 220.127.116.11.0 - 64bit Production
With the Partitioning, OLAP and Oracle Data Mining options
JServer Release 18.104.22.168.0 - Production