Title: Macintosh operating systems
Content:  technologies compared to its competitors. The current Mac operating system is macOS, originally named "Mac OS X" until 2012 and then "OS X" until 2016. Developed between 1997 and 2001 after Apple's purchase of NeXT, Mac OS X brought an entirely new architecture based on NeXTSTEP, a Unix system, that eliminated many of the technical challenges that the classic Mac OS faced. The current macOS is preinstalled with every Mac and is updated annually. It is the basis of Apple's current system software for its other devices – iOS, iPadOS, watchOS, and tvOS. Prior to the introduction of Mac OS X, Apple experimented with several other concepts, releasing different products 
Title: Operating system
Content:  macOS (formerly "Mac OS X" and later "OS X") is a line of open core graphical operating systems developed, marketed, and sold by Apple Inc., the latest of which is pre-loaded on all currently shipping Macintosh computers. macOS is the successor to the original classic Mac OS, which had been Apple's primary operating system since 1984. Unlike its predecessor, macOS is a UNIX operating system built on technology that had been developed at NeXT through the second half of the 1980s and up until Apple purchased the company in early 1997. The operating system was first released in 1999 as Mac OS X Server 1.0, followed in March 2001 by a client version (Mac OS X v10.0 "Cheetah"). Since then, six more distinct "client" 
Title: Macintosh operating systems
Content:   macOS (originally named "Mac OS X" until 2012 and then "OS X" until 2016) is the current Mac operating system that officially succeeded the classic Mac OS in 2001. Although the system was originally marketed as simply "version 10" of Mac OS, it has a history that is largely independent of the classic Mac OS. It is a Unix-based operating system built on NeXTSTEP and other technology developed at NeXT from the late 1980s until early 1997, when Apple purchased the company and its CEO Steve Jobs returned to Apple. Precursors to the original release of Mac OS X include OPENSTEP, Apple's Rhapsody project, and the Mac OS X Public Beta. macOS makes use of the BSD codebase and the XNU kernel, and its core set of components is based upon Apple's open source Darwin operating system. macOS is the basis for some of Apple's other operating systems, including iPhone OS/iOS, iPadOS, watchOS, and tvOS.
Title: Macintosh
Content:  to various companies through Apple's Macintosh clone program from 1995 to 1997. Only one company, UMAX Technologies, was legally licensed to ship clones running Mac OS 8. In 2001, Apple released Mac OS X, a modern Unix-based operating system which was later rebranded to simply OS X in 2012, and then macOS in 2016. Its final version was macOS Catalina, as Apple went on to release macOS Big Sur in 2020. The current version is macOS Monterey, first released on June 7, 2021. Intel-based Macs can run native third party operating systems such as Linux, FreeBSD, and Microsoft Windows with the aid of 
Title: Comparison of user features of operating systems
Content:  MacOS previously Mac OS X and later OS X) is a series of proprietary graphical operating systems developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop, laptop and home computers, and by web usage, it is the second most widely used desktop OS, after Microsoft Windows. macOS is the direct successor to the classic Mac OS, the line of Macintosh operating systems with nine releases from 1984 to 1999. macOS adopted the Unix kernel and inherited technologies developed between 1985 and 1997 at NeXT, the company that Apple co-founder Steve Jobs created after leaving Apple in 1985. Releases from Mac OS X 10.5 Leopard and thereafter are UNIX 03 certified. * Apple's mobile operating system, iOS, has been considered a variant of macOS. Mac OS 
Title: MacOS
Content:  macOS (previously Mac OS X and later OS X) is a proprietary graphical operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and laptop computers it is the second most widely used desktop OS, after Windows NT and ahead of Chrome OS. macOS succeeded the classic Mac OS, a Macintosh operating system with nine releases from 1984 to 1999. During this time, Apple cofounder Steve Jobs had left Apple and started another company, NeXT, developing the NeXTSTEP platform that would later be acquired by Apple to form the 
Title: MacOS version history
Content:  The history of macOS, Apple's current Mac operating system formerly named Mac OS X until 2012 and then OS X until 2016, began with the company's project to replace its "classic" Mac OS. That system, up to and including its final release Mac OS 9, was a direct descendant of the operating system Apple had used in its Macintosh computers since their introduction in 1984. However, the current macOS is a Unix operating system built on technology that had been developed at NeXT from the 1980s until Apple purchased the company in early 1997. Although it was originally marketed as simply "version 10" of the Mac OS (indicated by the Roman numeral "X"), it has a completely different codebase 
Title: MacOS
Content:  dark user interface option and a dynamic wallpaper setting. It was succeeded by macOS 10.15 Catalina in 2019, which replaces iTunes with separate apps for different types of media, and introduces the Catalyst system for porting iOS apps. In 2020, Apple previewed macOS 11 Big Sur at the WWDC 2020. This was the first increment in the primary version number of macOS since the release of Mac OS X Public Beta in 2000; updates to macOS 11 were given 11.x numbers, matching the version numbering scheme used by Apple's other operating systems. Big Sur brought major changes to the UI and was the first version to run on the ARM instruction set. The new numbering system was continued in 2021 with macOS 12 Monterey.
Title: Macintosh operating systems
Content:  released to end users on Monday, September 25, 2017 ; macOS Mojave – version 10.14, released to end users on Monday, September 24, 2018 ; macOS Catalina – version 10.15, released to end users on Monday, October 7, 2019 ; macOS Big Sur - version 11, released to end users on Thursday, November 12, 2020 ; macOS Monterey - version 12, released to end users on Monday, October 25, 2021. The first desktop version of the system was released on March 24, 2001, supporting the Aqua user interface. Since then, several more versions adding newer features and technologies have been released. Since 2011, new releases have been offered on an annual basis.
Title: MacOS Monterey
Content:  macOS Monterey (version 12) is the 18th and current major release of macOS, Apple's desktop operating system for Macintosh computers. The successor to macOS Big Sur, it was announced at WWDC 2021 on June 7, 2021,  and released on October 25, 2021. The operating system is named after Monterey Bay, continuing the trend of releases named after California locations since 2013's 10.9 Mavericks.

Question: what is the current mac os operating system?
Answer: 10.13.4.
macOS High Sierra.