A quarter of a century ago today, Apple introduced a brand new operating system to the world as a successor to Mac OS 9, the press release for this is still up on Apple’s website to this day. It replaced the base code and entire underlying system which all Mac OS versions were previously based on. As the codebase was aging, Mac OS 9 was considered to be increasingly unstable, had a less effective memory management style, and ultimately wasn’t able to deliver the kind of functionality that Mac OS X was able to. Mac OS X was based off of NeXTSTEP, an operating system that came from Steve Jobs’s prior company: NeXT, Inc. Mac OS X 10.4 Tiger was a significant foundation for the early development of iPhone OS – a lot of today’s core iPhone software stemmed from the same base. This article touches on bits and pieces of history, the wider impacts of Mac OS X, and where it is today.

Why Steve Jobs started NeXT, Inc

Despite being a founding member of Apple, Inc, Steve was fired before returning as CEO in 1997 as a result of a power struggle between himself and John Sculley in 1985. The board perceived him as confrontational, interpersonally difficult, with Jobs claiming he was fired, whereas Sculley claimed he quit after expressing his frustrations to the board. Sales expectations weren’t met by the Lisas and the Macintoshes so as a result, Steve Jobs was pushed out of the Macintosh project. This of course, made Jobs flustered.

NeXT, Inc. focused on education and business-class workstations and later got into developing for the web. While NeXT computers had limited commercial success, the influence of NeXTSTEP’s GUI as well as how it was programmed set the bar on computer innovations. Apple and NeXT merged in 1997 which included 1 and a half million Apple stock shares, and a $427 Million deal. At first he moved onto an advisory role, before becoming the CEO of Apple in ’97. Games like Doom and Quake trace their lineage back to NeXT, in addition to the world’s first ever web browser: WorldWideWeb. (NeXT, Wikipedia, Wikimedia Foundation, 11/8/24, URL)

The revival and regrowth of Apple

From Steve Jobs’s return to Apple, to the Bondi Blue iMac, the subsequent introduction of colorful options on Macs, and then to the introduction of this new OS in 2000: Mac OS X marked a pivotal turning point for Apple. Not only it rejuvenated the Mac vs PC rivalry (remember Hi, I’m a Mac..?), it created ripple effects in the wider computer industry. Apple was nearing bankruptcy in the late ’90s, and this new interpretation of the Macintosh Operating System was both symbolic and representative of the direction Apple was steering into after Jobs’ return in 1997.

According to an article by The Verge: “Microsoft created a secret Windows XP theme that made the operating system look more like a Mac. A recent Windows XP source code leak has revealed Microsoft’s early work on the operating system and some unreleased themes the company created during its early XP development back in 2000.” (Microsoft had a secret Windows XP theme that made it look like a Mac, The Verge, 9/25/2020, URL)

Evidently, Mac OS X had a substantial impact on the development of Windows XP! While the final “Luna” theme didn’t look like Aqua, it certainly drew it’s inspiration from or was invigorated by Apple’s Aqua.

(Above: Screenshot of Windows XP with Aqua theme, from The Verge)

The Darwin Kernel

The Darwin kernel is the core part of Apple’s Darwin OS, which serves as the foundation for macOS, iOS, and other platforms by Apple. It’s maintained to this day, the latest stable release being on December 2024 at the time of writing this article, as version 24.2 for macOS Sequoia 15.2. Darwin was constructed as a hybrid between the Mach 3 microkernel, with bits and pieces of BSD Unix – which gave Mac OS X protected memory, a secure core, and brought true multitasking to Macs.

Mach being a part of the kernel means Mac OS X gained some critical underlying features, too: VMM (virtual memory management) as well as process communication. One of the biggest complaints about the classic Mac OS was how app crashes often led to system-wide crashes. Though memory management improvements were made for this issue in Mac OS 9.1, this didn’t solve the problem entirely. Darwin was announced as an open-source project in order to appeal to Unix/open-source developers for Macs. Device drivers were also now made in a new I/O kit.

Out goes Platinum, in goes Aqua

While the original version of the aqua interface stuck around up to Mac OS X 10.2.8 Jaguar, bits and pieces of it remained all the way through OS X 10.9 Mavericks. OS X Mavericks was the final operating system to have elements of Aqua (or rather, a refined Leopard-Lion-ified version of it), before the release of OS X Yosemite which introduced a modern “flat” theme alongside iOS 7. Panther (10.3) was the first version of Mac OS X to have iterations on Aqua, introducing a “brushed metal” kinda look. Mac OS X Tiger took this a step further and made refinements on this theme. Mac OS X Leopard made everything look more modern which set the tone for successive releases, with OS X Lion iterating on the “Leopard-ified” style further.

(Above: Mac OS X 10.2 Jaguar)

(Above: Mac OS X 10.4.11 Tiger)

(Above: Mac OS X 10.5.8 Leopard)

(Above: OS X 10.9.5 Mavericks. Screenshot from Reddit user mezilga: URL)

It led to the development of the iPhone

In what originally started in 2004 as “Project Purple”, the version of iOS we use today was among one of the competing versions of the “iPhone OS”. One version of the iPhone project was based more off an iPod nano, the other was a multitouch device that eventually became the original iPhone. Building upon the Mach microkernel, BSD, Darwin, and underlying technologies offered by Mac OS X Tiger such as Cocoa, iPhone OS (now iOS) shares code with macOS. The Cocoa framework was adopted to multitouch (called Cocoa Touch), and Core Animation (introduced in Tiger) is what allowed for the smoothness/fluidity of iOS UI animations. If you’re using an iPhone, you’re using a Mac.

(Above: Screenshot from DigitalTechTrends video thumbnail “Evolution of iOS“)

Fast forward to 2025: Overall iPhone sales for Q1-Q4 2024 was $201.18 Billion. More than 1.382 billion consumers use iPhones right now, Apple shipped 151.3 million iPhones in Q1-Q3 of 2024, has a 53% market share in the US, 17% global market share, and on top of all this: 4/10 most-sold smartphones in Q3 2024 were designed by Apple. (iPhone users and sales stats, backlinko, 12/10/24, URL)

Other direct or indirect industry impacts

• While tablet computers existed well before the iPad.. the release of the iPad in 2010 (which ran a version of iPhone OS 3) set the bar for how tablets would be made thereafter.
• watchOS wasn’t the first to the smartwatch market, being released almost an entire year after the LG G watch. This never stopped Apple Watches from being the most successful smartwatches according to market data.
• Before the iPhone: Although Android has been around since 2003, it was first developed for digital cameras before shifting to phones. Reportedly, Google engineers scrapped their blackberry-like phone in favor of a touch-based OS, which pushed back development/release for an entire year.
• To put it mildly and quote an excerpt from The Atlantic: “As a consumer I was blown away. I wanted one immediately. But as a Google engineer, I thought ‘We’re going to have to start over.” (The Day Google Had to ‘Start Over’ on Android, The Atlantic, 12/18/2013, URL)

(Above: Picture from Apple Insider. Link to article)

macOS Today

The latest and greatest stable release of macOS at the time of writing this article is version 15.2, with 15.3 in beta. Long gone are the days of the Aqua theme, skeuomorphic design, Rosetta 1, and Classic. Despite older versions being far out of support and development, older macOS versions remain popular with enthusiasts due to their stability, nostalgia, appearance, and relatively wide array of application support. App support is better on older Intel builds versus older PowerPC builds, but this doesn’t stop anyone from enjoying the good ol’ Mac OS X Tiger or Leopard. Snow Leopard was a big hit and remains highly acclaimed. Today’s macOS thematically iterates off the changes introduced in macOS Big Sur, which itself was a thematic iteration of the “flat” design introduced in OS X Yosemite.

The latest and greatest macOS Sequoia continues introducing new features to macOS, is able to run on supported Intel Macs in addition to Apple Silicon Macs, and can be patched via OCLP to run on unsupported Macs.

• It introduces Apple Intelligence, an updated Siri, iPhone mirroring, iPhone notifications on the Mac, seamless dragging/dropping between the iPhone and Mac, native window tiling for the Mac, presenter preview, Safari highlights, a smarter safari reader, a new safari video viewer, a passwords app, new ways to play with text messages in the messages app, and more.
• Mac sales reached $7.74 billion in Q4 2024, accounting for 8.15% of Apple’s total quarterly revenue (Source: backlinko)
• In Q3 2024, Apple shipped 2.8 Million Macs which accounted for 15.8% of the market share. It’s currently sitting as the 4th largest “PC” vendor in the US. This can be attributed to the release of the M3 MacBook Air and back to school promos.
• While this doesn’t at all factor in the release of newer Macs such as the M4 Mac mini, M4 MacBook Pros and the M4 iMac, it’s safe to assume there will be more growth.

(Source: Canalys / Patently Apple)

(Click to enlarge image of MacBook Air running macOS Sequoia. Source: SixColors)

At the time of writing this article, Apple is on the verge of becoming the very first company valued at or over $4 Trillion USD market capitalization. It’s currently the most valuable company in the world, is worth $3.6 Trillion, after reaching a height of $3.86 Trillion on 12/27/2024. It was the first U.S. company to reach a market capitalization of $1 Trillion, achieving this on August 12th, 2018.