Alexosh1234, teaches you how to jailbreak your iPhone 3GS on a Mac or a PC. You will need the 3.0 firmware and the program Purplera1n. Download it, install it and run it. Connect the iPhone 3GS to the computer and click Make it rain in the Purplera1n program. Make sure iTunes is closed. Close it if iTunes starts during the jail-breaking process. Wait for it to finish. It will power off and then on and you can go to the home screen and see a Freeze application. Tap that and tap install Cydia. Reboot your iPhone and then you will see the Cydia application icon on the home screen. The jailbreak is now done.