Mac OS X 10.1

Mac OS X 10.1 (code named Puma) is the second major release of macOS, Apple's desktop and server operating system. It superseded Mac OS X 10.0 and preceded Mac OS X 10.2. Version 10.1 was released on September 25, 2001 as a free update for Mac OS X 10.0 users. 
The operating system was handed out for no charge by Apple employees after Steve Jobs' keynote speech at the Seybold publishing conference in San Francisco. It was subsequently distributed to Mac users on October 25, 2001 at Apple Stores and other retail stores that carried Apple products.
System requirements.
Supported computers:
RAM:
Hard Drive Space:
Features.
Apple introduced many features that were missing from the previous version, as well as improving overall system performance.
This system release brought some major new features to the Mac OS X platform:
Apple switched to using Mac OS X as the default on all then-new Macs with the 10.1.2 release.