System 4.1, Finder 5.5 (System Software 2.0.1) was officially introduced on March 2, 1987.
Mac users had just two months to enjoy a nice 1 digit version number of their operating system. System 4.1 was updated to work with AppleShare 1.1. AppleShare 1.1 was required to network the newly launched Macintosh II, which reportedly did not reach the market until April 1987. This update also modified the way the Finder handled large capacity drives (namely those larger than 32 MB).
System 4.1 also excluded the Mac 512K, as it required at least 1 MB of RAM to run. This was the last time Apple dropped hardware support for over a decade; they would not exclude further models until the introduction of Mac OS 7.6 which only ran on "32-bit clean" hardware.
- The develop CD and its spawn by Eric Rasmussen, Apple Macintosh before System 7. Archived 2011-11-22.
- Dates in Mac history by Lawrence I. Charters and Dr. Kathleen G. Charters, KLJCharters Blog. 2013-10-30.
- System 4.1 / Finder 5.5 (System Software 2.0.1), The Mac 512. Archived 2016-12-02.
- Macintosh: System Software Version History at Apple Support (2012-02-19)