TA24901: About the Mac OS X 10.4.11 UpdateLearn about About the Mac OS X 10.4.11 Update
Currently Being ModeratedFeb 10, 2013 4:59 AM (in response to sianytay)
Welcome to the Apple Support Communities
As you want to update your iPhone and iPad, you want iTunes 11.0.1, that requires Mac OS X Snow Leopard.
First, open > About this Mac, and see "Processor". If it's an Intel processor, you can upgrade to Snow Leopard, so buy it > http://store.apple.com/us/product/MC573/mac-os-x-106-snow-leopard
Then, make a backup of your data, insert the Snow Leopard disc and upgrade to Snow Leopard.
The DVD contains Mac OS X 10.6.3, so open > Software Update and install 10.6.8. Then, run Software Update again to install iTunes 11, so you will be able to sync the iPhone and iPad.
If you want, you can check if you can use OS X Mountain Lion > http://www.apple.com/osx/specs If you can use Mountain Lion, just open App Store and purchase it. Check if your applications are supported > http://www.roaringapps.com
Currently Being ModeratedFeb 10, 2013 8:50 AM (in response to sianytay)
If you have a PPC iMac OS 10.5 Leopard is as far as you can go.
If it is an Intel iMac - see the reply from mende1.