In 1997, Apple rebranded the Macintosh System Software to Mac OS. Only one application at a time could be supported under System Software until version 5 when MultiFinder was introduced. It uses a monolithic architecture but lacks support for memory management, protected memory, access controls, and conflict-free extensions. The original Macintosh System Software is based on the Lisa OS and UI concepts from Xerox PARC. PCE and Mini vMac are able to run 68k builds of Mac OS, QEMU is also capable of running earlier PPC builds of MacOS, and VirtualBox and VMware Fusion can run x86/64 builds of Mac OS X. PearPC is a useful emulator that can run PowerPC builds of Mac OS X under Windows or other x86 operating systems. Only certain versions of Mac OS 9 can run under the Classic system layer, and the layer itself was dropped after Mac OS X Tiger. The Classic Mac OS can run standalone, and under Mac OS X using the Classic system layer. Support for PowerPC in Mac OS X was dropped in 2009.Īt WWDC 2020, Apple declared that they would switch over to the Apple Silicon SoC in future Mac computers. In 2006, Apple switched to Intel-based x86 processors in Macs. In response, Apple bought NeXT and used NeXTSTEP as a base to develop Mac OS X. Classic Mac OS was based on a simple kernel design, which eventually became too limited and crash-prone for applications.

PowerPC would be used until the classic Mac OS's discontinuation in 2002.

The 68k architecture was used from 1984 to 1991, after which Apple transitioned to PowerPC. The classic Mac OS was originally written for the Motorola 68k architecture. It first became publicly available in 1984 with the release of the Macintosh 128k. macOS is the second-most commonly used operating system after Microsoft Windows. MacOS is a series of operating systems developed by Apple for their Macintosh platform. Closed source (with open source components)

Mac os 9 emulator for mac os sierra