Is My System running 32bit or 64bit OS?

Simple answer would be to check if you can find Dianosours around you, If you find it ; you're running 32bit OS.

For HPUX System:
/usr/bin/getconf KERNEL_BITS

Check the man page for more info about getconf(1) like: MACHINE_SERIAL,HW_CPU_SUPP_BITS

For Solaris Systems:
/usr/bin/isainfo -v
For more information please check the man page isainfo

For AIX Systems:
bootinfo -k

For RedHat Linux System:
getconf LONG_BITS

64bit Kernel will respond 64 else find the Dinasours.
Another way to check if the system is running 64bit kernel to check flag `lm` in `cat /proc/cpuinfo`