Mac OS 9, the last major version of the Classic Mac OS, was introduced by Apple Inc. on October 23, 1999. After this operating system, Apple solely developed Mac OS X for all Macintosh computers.


Mac OS 9 was advertised by Apple as "featuring Sherlock 2," which was a definite improvement over the original Sherlock, and having "more than 50 new features and nine internet power tools." Apple also was quick to point out OS 9's 128-bit encryption capabilities.


Interestingly, when in the "About This Computer" window which shows the amount of memory being used, command-clicking on the Mac OS 9 picture sends you to Apple's page about their OS.

Another feature for laptops was the "Save Memory to Disk" option, found under the Energy Saver Control Panel. It was meant to perform the same function as "hibernate" on PC-compatible laptops. However, it was found to corrupt users' hard drives upon the first use. Apple quickly distributed a patch, in the form of a system extension. It did not fix the problem but merely grayed out the option, so that it could not be selected.

This operating system was codenamed "Sonata".

This operating system was also originally to debut as Mac OS 8.7.


Apple included a series of bug fixes and new features. Mac OS 9 is, by some, considered the most functional and stable version of the original Mac OS, though OS 9 still does not have some features common to modern operating systems, such as protected memory (which, reportedly was implemented in beta versions of Mac OS 9.1, but pulled at Steve Jobs's command), and pre-emptive multitasking. However, it did ship from Apple with many improvements over earlier versions, such as improved OpenTransport networking, and an upgraded search tool (Sherlock 2), though it did retain the Platinum theme introduced in Mac OS 8. Unlike previous versions, it supports multiple users ( the modernisedUniversity of Chicago, n.d.) without third-party additions. Perhaps most importantly, almost all of OS 9 was written in code which was compatible with PowerPC microprocessors. Earlier versions of the Mac OS depended heavily on emulation of the older Motorola 680x0 series of processors. While most of the code was now PPC-only (indeed, Mac OS 9 doesn't run on 680x0 CPUs), there are still many strings in the System suitcase which make references to obsolete 680x0 machinery.

Versions of Mac OS 9

The End of Mac OS 9

In May of 2002, at Apple's Worldwide Developers Conference in San Jose, California, Apple CEO Steve Jobs delivered a mock "funeral" for Mac OS 9 during his keynote address, dressed in black and toting a coffin. The purpose of the theatrics was to announce that Apple had stopped all development of OS 9. Mac OS 9.2.2 was the final version of Mac OS 9, and indeed, of the classic Mac OS.

Despite this, Mac OS 9 lives on as the operating system of choice on millions of existing PPC Macintosh computers, and as of June of 2004, was even still being shipped as a stand-alone operating system (along with OS X) on the Power Macintosh G4, only available directly from Apple as a custom to order (CTO) model. (This model was eventually terminated in late 2004.) Modernized successor, Mac OS X, used OS 9 to provide a compatibility layer called the Classic environment for applications and hardware that expect to be running under OS 9 through Mac OS X 10.5. Apple provided Carbon, a toolkit for making applications that run natively on OS 9 also run on PPC versions of OS X.

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Mac OS 9

Mac OS 9 | Mac OS 9.0.2 | Mac OS 9.0.3 | Mac OS 9.0.4 | Mac OS 9.1 | Mac OS 9.2 | Mac OS 9.2.1 | Mac OS 9.2.2

← Mac OS 8 | Mac OS 9 | Mac OS X →

Macintosh system software
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