The Mac OS Recovery HD partition is a pretty handy troubleshooting tool that can also be used to reinstall or repair the Mac OS.
Managing the Resume Feature in the Mac OS
Identify the Version of Mac OS on the Recovery Partition
Create Your Own Mac Recovery HD on Any Drive
Jak korzystać z trybu samolotowego na telefonie iPhone i zegarze
How to Use the Mac's Auto-Save and Versions Feature
Managing the Resume Feature in the Mac OS
Create Your Own Mac Recovery HD on Any Drive
How to Use the Mac's Auto-Save and Versions Feature
Minimum Requirements for OS X Mountain Lion (10.8)
Mac Recovery HD Volume: Reinstall OS X or Troubleshoot