can I back up my entire iMac on iCloud

iCloud is designed to sync data from mobile devices. You can't back up your Mac to iCloud. Get an inexpensive external drive and either use the built in Time Machine app to back up your Mac, or clone your hard drive using a third-party application like Carbon Copy Cloner.

Thanks I was wondering the same. Just bought an iCloud subscription, was it worth it? I suppose I can at least back up my iTunes stuff? Any suggestions for decent inexpensive back up solutions would be great. I have iMac with latest OS, using 300GB out of 500GB.