Mac OS X version 10.5, or Leopard, is the latest major release of Apple's operating system for the Macintosh computer. It is the successor to Apple's last major operating system, Tiger and reportedly contains over 300 new features and enhancements.

Leopard was originally designated to be released sometime in 2005, but the deadline was pushed back in order to compete with Microsoft Windows Vista. However, the operating system was not released until October 2007 because of the iPhone development.

Leopard features many new features and enhancements such as the Time Machine and Spotlight. In total there were over 300 new features or enhancements added. There were also security enhancements such as an application layer firewall that blocks applications based on a filter rule. Leopard also features Application Signing, which makes developers have a key signature to verify that they had not been tampered with by a malicious person. Another highly touted feature is the secure guest feature, which allows a person to login to a computer as a guest. After the person logs out the account is erased so it cannot harm the computer.

Initially it was reported that some computers had a problem installing Leopard because of certain programs. This caused the computer to hang at boot with a blue screen. People were also concerned with Leopard's security settings, especially how the firewall and been weakened to a per-application basis. Time Machine was also criticized because it lacks certain features that make it comparable to many other 3rd party backup utilities.

1. Mac computer with an Intel, PowerPC G5, or PowerPC G4 (867MHz or faster) processor
2. 512MB of RAM
3. DVD drive
4. 9GB of hard drive space

• Guy Kawasaki: Top Ten Leopard Tips (October 30, 2007)