The History of Mac OS and macOS: System 1, NeXTSTEP and Apple Silicon

A computer for the rest of us, running one app at a time

On January 24, 1984, Apple put the Macintosh 128K on sale for $2,495, about $7,700 in 2025 dollars: a 9-inch monochrome display, 128 KB of RAM, a Motorola 68000 processor running at 7.8336 MHz, and a 400 KB 3.5-inch floppy drive, in a machine weighing 16.5 lb (7.5 kg). The launch came just days after “1984,” the ad directed by Ridley Scott for the Chiat/Day agency, aired nationally on January 22 during the third quarter of Super Bowl XVIII: Apple’s board had initially rejected it, and it was Steve Wozniak who offered to personally cover half the cost of the airtime just to see it broadcast. The ad would later enter the Clio Awards Hall of Fame in 1995 and top Advertising Age’s list of the fifty greatest commercials of all time; the Macintosh itself sold 70,000 units by May 3, 1984.

The operating system inside that machine, System 1.0, was deliberately minimal: it could run only one application at a time and relied on a flat file system, the Macintosh File System (MFS), with no nested folders, just a plain list of files. Behind the scenes was a small team that would go on to shape the history of personal computing: Andy Hertzfeld wrote much of the ROM, kernel and Toolbox code, Susan Kare designed the icons that made the interface instantly recognizable, and Bruce Horn and Steve Capps built the Finder. Steve Jobs had taken over the Macintosh project in 1981 from its original leader, Jef Raskin, while Apple’s other co-founder, Steve Wozniak, was on leave during the project’s most critical development phase.

Later versions arrived quickly. System 2.0 (April 1985) added support for AppleTalk networking and the LaserWriter printer, and introduced the screenshot shortcut Cmd+Shift+3. System 2.1, a few months later, brought in HFS (Hierarchical File System), the file system that would replace MFS, while System 4.0 in 1987 added the first color support. The real turning point was System Software 5 (October 1987), the first Mac OS package sold at retail, which introduced the MultiFinder: for the first time, more than one application could stay open at once, though multitasking was still “cooperative,” meaning it depended on each program’s willingness to hand control of the processor back and forth. That’s a very different mechanism from a modern operating system with preemptive multitasking, where a scheduler algorithm decides, moment by moment, which program gets control of the processor.

Practical example: picture working in 1988 on a Macintosh with System 6 freshly installed, running a spreadsheet and a word processor side by side thanks to the MultiFinder. If one of the two programs freezes without handing control back to the system, the other stops responding too. That’s exactly what “cooperative” means in the MultiFinder’s name: the two programs coexist only as long as they behave, not because the operating system enforces any separation between them.

From System 7 to Mac OS 9: the classic line’s long chase

System 7, released on May 13, 1991, was the most ambitious overhaul of the classic line: it introduced native virtual memory support, 32-bit addressing, a MultiFinder that was now permanent rather than optional, scalable TrueType fonts, and the AppleScript automation language. With System 7.1 in 1992, the first Mac OS version sold as a standalone product, fonts moved into a dedicated folder, and the 7.1.2 update brought the first support for the new PowerPC processors, running alongside the older Motorola 68k chips for years. System 7.5 in 1994 folded in many features that started out as shareware Apple had acquired, but it suffered stability problems on PowerPC machines.

In 1997 the word “System” dropped out of the name: Mac OS 7.6 was the first release simply called “Mac OS,” and it dropped support for the original Motorola 68000 processors. A few months later came Mac OS 8 (July 26, 1997), with a multi-threaded Finder and a new look called “Platinum”: it sold 1.2 million copies in its first two weeks and 3 million within six months of launch. Mac OS 8.1 introduced the HFS+ file system and USB support, while remaining the last version compatible with 68k chips; versions 8.5 and 8.6, which by then required PowerPC processors only, added the Sherlock search tool, FireWire support and a redesigned “nanokernel.” Mac OS 9, on October 23, 1999, was the classic line’s final major release: it brought support for AirPort wireless networking, the first multi-user features, file encryption and the Keychain password manager, and introduced the Carbon APIs, built specifically as a bridge to the operating system that would come next. The family’s last update, Mac OS 9.2.2, shipped on December 5, 2001, by which point Mac OS X had already been unveiled.

Version	Year	Main innovation
System 1.0	1984	Single application, flat MFS file system
System Software 5	1987	MultiFinder, cooperative multitasking
System 7	1991	Virtual memory, 32-bit addressing
Mac OS 8	1997	Multi-threaded Finder, Platinum look
Mac OS 9	1999	AirPort, Keychain, Carbon APIs
Mac OS X 10.0 Cheetah	2001	Darwin kernel, NeXTSTEP legacy
Mac OS X 10.6 Snow Leopard	2009	First Intel-only release
macOS 11 Big Sur	2020	First Apple Silicon support
macOS 26 Tahoe	2025	Numbering aligned with the calendar year

Jobs’ return, and the technology Apple actually needed

While the classic line kept aging, Apple had spent years trying to build a more modern successor with an internal project called Copland, which never reached completion. The fix came from an unexpected direction: in September 1985, after months of being gradually pushed out of company decisions, Steve Jobs resigned from Apple and founded NeXT, promising the board he would not compete directly with the company he had helped create. Under engineer Avie Tevanian, NeXT built NeXTSTEP, an operating system with an object-oriented architecture and a graphical interface well ahead of its time; the company later teamed up with Sun Microsystems to create OpenStep, designed to separate the application layer so it could run on other companies’ operating systems too.

With Copland effectively dead, Apple announced on December 20, 1996 that it would acquire NeXT, a deal that closed on February 7, 1997. The price Apple paid, in cash, stock, stock options and assumed debt, came to $427 million; Jobs personally received 1.5 million shares of Apple stock, even though he would have preferred to be paid entirely in cash. His return to the company wasn’t immediate: he came back first as an advisor, then became interim CEO on September 16, 1997, and only took the job full-time in 2000. Tevanian, who had been vice president of engineering at NeXT, followed him to Apple, and his work proved decisive in bringing the technology that would become the foundation of Mac OS X in-house.

Mac OS X: the technical leap, and three architecture changes

Mac OS X 10.0, code-named “Cheetah,” debuted on March 24, 2001, built on the hybrid Darwin kernel (version 1.3.1), based on Mach with roots in FreeBSD and compliant with POSIX standards, a Unix-based technical foundation, different from the classic line it was replacing. From there Apple shipped almost one version a year for more than two decades: Puma (2001), Jaguar (2002), Panther (2003), Tiger (2005), Leopard (2007), Snow Leopard (2009), Lion (2011), Mountain Lion (2012), Mavericks (2013), Yosemite (2014), El Capitan (2015), Sierra (2016), High Sierra (2017), Mojave (2018) and Catalina (2019), followed by the more recent name changes: Big Sur (2020), Monterey (2021), Ventura (2022), Sonoma (2023) and Sequoia (2024).

Behind that string of names runs a parallel story, the one about the processor, part of the same broader arc traced by the history of computers more generally. Mac OS X 10.0 ran only on PowerPC chips, inherited from the classic line since 1994; the first Intel-based Macs arrived in 2006, running a specialized version of Tiger, and the following year Leopard introduced “universal binaries,” capable of running natively on both PowerPC and Intel. In 2009, Snow Leopard became the first Intel-only release, closing out the second processor architecture transition in the Mac’s history (the first, from Motorola 68000 to PowerPC, dated back to 1994).

Practical example: someone who upgraded a PowerPC Mac to Mac OS X Leopard in 2007 could keep using most of their existing software, thanks to universal binaries. Someone who tried installing Snow Leopard on that same PowerPC Mac two years later, though, was simply out of luck: that release required an Intel processor, no exceptions.

The third transition came later, and Apple’s own words tell it best: on June 22, 2020, at WWDC, CEO Tim Cook announced the move to processors designed in-house by Apple, saying, “Today we’re announcing our transition to Apple silicon, making this a historic day for the Mac.” The first Macs with the M1 chip, the Mac mini, MacBook Air and 13-inch MacBook Pro, arrived on November 10-11, 2020, alongside two technologies meant to soften the transition: Rosetta 2, which dynamically translates apps written for Intel so they run on the new ARM chips, and the “Universal 2” format, which lets developers build a single app that runs natively on both Apple Silicon and Intel Macs. Cook’s announced plan called for roughly two years to complete the transition across the whole Mac lineup; the actual process wrapped up on June 5, 2023, when Apple introduced the Mac Pro with an M2 Ultra chip, the last Intel-based model left to be replaced.

The new yearly naming, and where macOS stands in the market

In 2025, macOS also changed how it counts its versions. Until 2019 the system had stayed on the 10.x scheme, from Cheetah (10.0) to Catalina (10.15); in 2020, Big Sur broke that pattern by becoming simply “macOS 11,” followed by Monterey (12), Ventura (13), Sonoma (14) and Sequoia (15). With macOS 26 “Tahoe,” released on September 15, 2025, Apple made a second leap, aligning the version number with the calendar year: the 2026 release, code-named “Golden Gate” and numbered 27, was still upcoming as of when the sources for this Recap were checked, but it’s already described as the last version to offer full Rosetta 2 support, with Tahoe billed as the last release able to run on Intel-based Macs.

More than four decades after that 1984 Macintosh 128K, macOS still plays second fiddle in the desktop and laptop computer market compared with Apple’s longtime rival: as of April 2026 it was the second most widely used operating system in that segment, behind Microsoft Windows — whose own story, which started as a graphical shell running on top of MS-DOS, is told in the history of Microsoft Windows — and ahead of every Linux distribution combined.