A
Is there any software available which can know whether the cpu is running on ac or battery. And give warning messages or shutdown the system automatically.
software required
You are talking about Laptop or Desktop and if you are talking about desktop then is UPS being called as battery here? Sorry is not clear for me.
A
well, in case of desktops, APC ups comes with good s/w called Powerchute.
All the UPS today (for Desktop PCs) hv an indicator LED tellin u wehter its running on battery mode or on direct line current. There is no big deal about finding the s/ware bro 
u get the manual with every UPS that u buy, so from that u can find out on wat state ur UPS is running...
cheers n e-peace......
u get the manual with every UPS that u buy, so from that u can find out on wat state ur UPS is running...cheers n e-peace......
Checkout the softwares bundled with ur laptop!